Hello PPD.

Issues of this sort are, unfortunately, more common and the we'd like them to be. However, they tend not to be cause by Firefox itself, but rather by software that is running either inside or alongside it, such as add-ons or firewalls. Since these issues have a broad span of possible causes, you need to diagnose your problems before fixing them. Follow these instructions to the line, as they'll probably help you diagnose and fix the problems you're having.

1. run Firefox in safe-mode to disable all extensions, themes and plugins. If this fixes your problem, be it with RAM or CPU usage, then you know it's a problem with add-ons (plugins, themes or extensions). Proceed to number 2. If safe-mode doesn't fix your problem, then read bellow, after this list;
2. update all extensions (go into Tools > Add-ons > Extensions > Find Updates), themes and plugins (see this page in your Firefox. If this doesn't solve the issues, proceed to the following number;
3. disable all extensions, themes and plugins in your Firefox (not running safe-mode). This is temporary and for diagnostic purposes only. Being certain that, as in safe-mode, the problems you're having have gone away, enable one plugin at a time. You should be certain that you acutally want that plugin to be enabled. It's best to keep the overall number of enabled plugins as low as possible. When you encounter problems, you know you've found a problematic plugin, so disable it for good. Keep enabling all plugins (except problematic ones) until you've gone through them all. If you need support for a problematic plugin, you need to contact its author for support;
4. enable one extension at a time. Again, be certain that you actually want that extension to be enabled. As with plguins, it's best to keep the overall number of enabled extensions as low as possible. Also, try the theme you want to have installed so see if that is what's causing the problem. When you encounter problems, you know you've found a problematic extension/theme, so disable it for good. Keep enabling all your extensions (except problematic ones) until you've gone through them all. Just the same as with plugins, if you need support for a problematic extension/plugin, you need to contact its author;
5. if you've followed my instructions above, you're done! You've fixed your problems with problematic add-ons. If you want to keep using those problematic add-ons, please contant their authors for support.

Ok, now... If disabling all extensions and plugins through safe-mode didn't work to fix your problems (or, in other words, if you've just read number 1 on the list above and come straight here), then you have different issue. The most likely scenario is that you have a third party software running on your computer that is messing with Firefox. Detecting which program it is may be tricky, but the following list should help you. Make sure you follow it carefully. Don't forget to answer the question on the last point, if nothing else helps.

1. try reinstalling Firefox. No data will be lost. You can get the latest version (for free, as always) at getfirefox.com. Make sure you uninstall Firefox prior to reinstalling it. For help installing Firefox, see this support article. If that doesn't fix the problem, proceed;
2. do a virus/malware check on your computer. See this support article for help on this point. This is a very important step, so please pay attention to it. If your problem is not due to viruses/malware, proceed;
3. disable all software running in the background that you don't want to have running in the background (in Windows operating systems, this is done by pressing WINDOWS+R in your keyboard, typing msconfig and pressing Enter; now, under the Startup tab, you can uncheck the software you don't want, and reboot your system for changes to take effect; if you're unsure of what software you want running, ask someone with more experience). If this doesn't fix your issues with Firefox, proceed;
4. check if your firewall/antivirus/security suite is conflicting in any way with Firefox's normal behavior. Check for enabled functions/features that you don't want and/or may be causing problems with Firefox. You'll find that these features are most likely tied to Internet Security features, such as link scanners or URL checkers and the like. If you're not sure they are conflicting with Firefox, simply try to disable them temporarily to see whether or not that's true. If this doesn't solve the issues, proceed to the following number;
5. check your operating system security options, mainly advanced options that are not configured by default. While it's very unlikely that this may be the cause of the problem, it's remotely possible. If this doesn't work, proceed to the following point;
6. update your modem/router software. There have been some reports that some modem/router software may cause Firefox and other browsers to loose performance and/or stability. If updating doesn't fix your issue, try other versions of the software, if possible. If you need support with this, contact your modem/router manufacturer. If this doesn't help, proceed;
7. if you are using a Windows operating system, clean up your OS registry using appropriate software. There have been reports that badly maintained Windows Registries may case problems with Firefox. If this doesn't help, see the following point;
8. please try creating a new temporary Firefox profile (managing profiles) and see if the issues persist. Please report the results, so we can help you further.

Thanks for your response.

I have to say that it looks canned and doesn't once take into account that this problem did not occur until after I upgraded Firefox.

So, whether or not the problem involves another piece of software, in or out of Firefox, the change of Firefox versions is the cause of the problem.

Now, since I have neither the time nor the inclination to determine why the latest version of the software is messed up, there are only two reasons to post the issue up here. First, that there is an known solution to what appears to be a common problem with the latest version and second, that others with similar issues may also discover the solution.

Now, since that first post, I found a download of the older 3.5.10, I'm going to try that and report back here. I'd like it to work since I quite like Firefox.

If this doesn't work, I'm going to look for another browser. It takes less time to install a new program than to debug a problematic one. Like most people I switched from IE because of the vulnerabilities. To switch again to a more reliable software would only require a change in my workflow, not an investment of time for which all I get is the working product I expected in the first place.

)ensen.

PS: When I think back on it, I think I may have been using an even earlier version of 3.x before the upgrade but I just don't keep track of these things.

"I have to say that it looks canned and doesn't once take into account that this problem did not occur until after I upgraded Firefox." It is canned, yes (can you imagine writing page long replies for so many users? I'd end up helping about 10% I'm able to help right now.

But it does take into account that the problem occurred after the upgrade. The thing is, it's completely irrelevant: add-ons (that's extensions, themes and plugins) are made for the browser, not the other way around. The add-on has to be compatible with the browser, not the browser with the add-on.

Other than that, if you don't try what I ask you to try, I can't be of much help, unfortunately.

"First, that there is an known solution to what appears to be a common problem with the latest version and second" It's not a common problem at all. Millions of users are using Firefox without trouble (otherwise it would be all over the news, support.mozilla.com would be flooded and the million (that's right, one million) beta testers of Firefox 3.6.4 would have noticed it), I myself included. With Flash and other plugins and extensions and whatnot, yes.

Please work with me to fix this problem, and I'll give my best to help you. Thank you for your understanding.

Thanks Morbus.

Time has been tight but I finally got around to installing 3.5.10 earlier today and it has been working flawlessly, with maybe 60-70MB usage even with 20 tabs open (this is typical for me when I am lurking and posting on various web forums).

I hope this wasn't too much of a waste of time for you, Morbus. The problem is that there just isn't time for me to spare on this. My initial hope was that there was already some kind of hot fix that could be applied.

Still, I do have some extra info for you in case it might help the programmers.

While I still had 3.6.6 installed earlier this week, I had been trying out different add-ons (BarTab, Gmail Notifier, Leak Monitor and Webmail Notifier). By the time I downgraded today, all had been disabled because I didn't like how they worked. In the case of Leak Monitor it did show me that a number of memory usages were not being freed up, even after I would clear history and close all tabs except Google. Even after rebooting with those 4 plug-ins shut down, the RAM continued to drain.

It is interesting to note that while downgrading did not change my add-on complement, it did stop any leaks. That's a pretty sure bet that the installed add-ons are not causing the problem.

If I had to guess, I might wager that the so-called Plug-In Containment system of 3.6x is what's causing these memory leaks. With the change back to 3.5.10, the process disappeared from Task Manager and any memory leaks went with it. Maybe it has something to do with the fact that this is a tablet and runs extra drivers and software for the digitizer and handwriting recognition.

Anyway, thanks again. I'm glad 3.5.10 works as I really didn't want to go looking for a new browser.

"I hope this wasn't too much of a waste of time for you, Morbus." Not at all, I'm glad you found a solution. Hopefully when Firefox 3.5 stops being supported there will be an update that fixes this problem.

"It is interesting to note that while downgrading did not change my add-on complement, it did stop any leaks. That's a pretty sure bet that the installed add-ons are not causing the problem." Do you think so? Just because an add-on works ok for a version doesn't mean it will work ok for another one. I'll give you some examples. Malware that is developed to target Firefox 3.5 works "perfectly" with 3.5, and doesn't cause any problem. But as soon as the user updates to 3.6, some malware is known (stress on the known part) to crash Firefox, because it simply won't work with the new version. I remember a few years, DownThemAll! (a download manager extension for Firefox) working correctly with Firefox 2.0, but with Firefox 3.0 it wouldn't download at all, simply because the author hadn't updated it correctly. This is extremely common for pre-release versions of new Firefoxes, of course, and very very rare with stable versions, but you can't rule it out until you rule it out. It's a matter of doing responsible and accurate troubleshooting. Otherwise you can't gather any conclusions whatsoever.

"Maybe it has something to do with the fact that this is a tablet and runs extra drivers and software for the digitizer and handwriting recognition." Maybe, Firefox 3.0.2 used to always crash on tablets. That was fixes for 3.0.3 and above. That was a long time ago, sure, but maybe it's just a harder platform to develop for.