Please explain a bit more what's happening. What slider? Which window?

Normally, the FF window will have a vertical scrollbar with a slider on the right side of the screen, allowing up and down scrolling when one screen in not enough to contain all the information presented by the website.

There may also be a horizontal scrollbar with a slider on the bottom of the screen, allowing left/right scrolling to access information off-screen to the right or left, as for instance when there is a large spreadsheet with columns that extend beyond the width of the screen.

In either case, when I place the cursor on the slider to scroll the screen up or down, or left or right and click the mouse holding it down while I move the slider, the slider disappears.

Sometimes it returns later, after releasing the mouse, sometimes not. I haven't yet been able to notice a pattern.

But I need the scrollbar/slider to efficiently access on-screen information. The Arrows just are not as useful.

Any suggestions?

Are you using the NoSquint extension? Some problems have been reported with that.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Problem solved: I have been using Walnut for Firefox ver. 2.0.28 theme. For some reason this has been causing the problem. Started FF in Safe Mode, and the slider problem disappeared. Then proceeded to re-enable the Walnut theme: the problem reappeared. Disabled Walnut theme and reenabled all my other add-ons (about 6 of them). Still no problem. So, clearly there is a problem with the use of Walnut theme in FF ver. 32, at least on my Windows 7 installation.

Thanks for all your suggestions and help. Good job, all!