I'm using Firefox 7 on Ubuntu 11.10. I am not definitely sure that this problem began since upgrading Ubuntu from 11.04, but that would be my guess.
The problem is fairly simple. Firefox freezes at random times, and when it does, it freezes the whole desktop with it.
I have tried removing every single plug in I have, and the problem persisted. I tried installing them back in one by one to see if any was more problematic than the rest, but no plug in emerged as a clear candidate.
I have tried to discern a pattern. I thought the most likely culprit would be video, like when on YouTube, but that isn't it. Sometimes it happens when I haven't even gone to a web page yet, and I just click to open the bookmarks drop down from the menu.
I would try running
firefox -debug from the command line, but the problem is once Firefox freezes, the desktop becomes completely inaccessible. I can still move the mouse, but I can't click on anything on the screen. I can't alt-tab between applications. All I can do is hit
ctrl+alt+backspace and then log out.
Any help to diagnose this problem would be much appreciated. I don't mind using Chrome and Chromium (which are stable as rocks on my system), but I have some plug ins on Firefox I can't live without.