No Q--just an FYI. Wife has a customized Sager laptop, now several years old, running Win7. Firefox _had_ been running just fine. Then, in the last two months, it would frequently hang after failing to redraw part or parts of the screen. Sometimes elements of the screen would flash back and forth, from one side of the screen to the other.
Tried updating FF, tried full-reinstall of ZoneAlarm, tried a bunch of stuff.
What finally seems to have worked is to turn off the "hardware acceleration" video option in FF. Evidently some time in the recent past FF made some screen optimization changes that no longer worked with the PC's video drivers.