A friend sent me an MP3 link about a month ago, and I was confused when Firefox told me the file was corrupt. I figured it was just the server it was on. Then, I stopped being able to listen to music posted through Tumblr. I figured they just updated their player and broke something. Then I tried listening directly to an MP3 on another site tonight, and again, Firefox told me "Video can't be played because the file is corrupt." I dashed around to a handful of other sites and every single one of them told me the same thing when I tried to play an MP3 file. After doing some investigation, I learned that the Firefox team has tried to implement their own internal music playback system that either can't find a codec or isn't detecting these files as music properly. Now, a long time ago, I got pretty used to all these files playing through Quicktime, to the point where I would specifically install Quicktime with each version of Windows just to restore this functionality. But now Firefox is overriding that functionality for some reason. The culprit seemed to be the option "media.windows-media-foundation.enabled", which I promptly disabled. Didn't help. Firefox is still insisting that these files are corrupt instead of letting Quicktime handle them. This site also suggested turning plugins.load_appdir_plugins to true, but that didn't help, either. It would seem Firefox is intentionally relying on a part of Windows that I don't have, because I'm still stuck on Windows XP (video capture hardware I depend on doesn't have drivers for Vista on up). The annoying part is that I can't seem to change it back to the way it was, and I'm pretty angry because this has broken a significant portion of the internet for me.