Firefox freezing and corrupting files

I've read some stuff about Firefox running slowly or freezing during page loads and such, so part of this may be old news.. but I'm actually getting freezes while it's NOT loading pages... For example, I'll be reading a page and scroll down. Firefox might freeze in mid-repaint. Now, anything that accesses the flash drive also freezes (read or write) and I can't kill the task via Process Explorer.

Another problem that I THINK is linked (possibly being caused by the freezes?) is that Firefox is corrupting files in it's directory. Mostly, it's been the cookies.sqlite and cookies.sqlite-journal, though it killed some extension files before.

When the second one happens, Firefox freezes more frequently, loses data, and if I remove / reinsert the drive, Windows asks me to scan the disk. Scandisk always finds a problem, and it's always under Firefox.

Now, I've been running with session restore on and cache off. I disabled session restore and it seems better, so far...

So... is this the same problem other people are having, or might I have flaky media?

Also, I saw some Fx 3.1 Speed Test stuff that came with disclaimers that it could make your profile unusable by future/previous versions... Did those changes make it into the 3.1 beta? i.e. would I likely get better performance and not screw up my profile by using 3.1?

Sorry this is so long, but thanks for reading it all