All keyboard input stops working after a few minutes. Ctrl-T, ctrl-f, home, end, all have no effect, and I can't type into forms, the find bar or the location bar. If I switch tabs or programs using the mouse, the problem stops briefly, and resumes a few minutes later.
The same problem happens in safe mode. Reinstalling the keyboard driver didn't help.
Firefox 3.6.8, Windows 7, laptop keyboard.