I have been having complete freeze-ups lately, about one (max. 2) per day (I use the computer for several hours a day). I started noting down which program I was using at the times when my machine freezes and so far every single time has turned out to be Firefox. I use a few other programs for extensive amounts of times and none of them were frontmost (or even running, I believe) when the freezes happened. This makes me think Firefox is the source or at least what triggers the freezes. The freezes happen randomly from what I am able to tell. They have happened right when submitting a form as well as when I am simply reading a page and not doing anything at all with the mouse or keyboard. This started happening before I upgraded to Firefox 4 (so with Firefox 3.6) but it has become a lot more frequent after I upgraded (which is why I started tracking the frontmost application at the times of the freeze-ups since I began to suspect that it was Firefox). The freeze-ups have manifested themselves in a few different ways so far: * everything on the screen "freezes" and any type of input, whether it's the keyboard command for force-quitting the frontmost application or clicking anywhere on the screen, has absolutely no effect. only the mouse cursor still moves * the same as above but I can't even move the mouse cursor * the screen goes blank * the screen turns white The last two may also appear with many thin vertical lines running across the screen.