brushes, erasers lag in photoshop cs4 64

I recently installed Photoshop CS4 64 bit, version 11.01. Even using a paintbrush 10 pixels across, the paint line lags a second behind the cursor. Same for similar tools like eraser and smudge.

My machine crashed yesterday and i got a blue screen saying there had been a clock error. (I didn't manage to get a photo before it disappeared.) I had been working in Photoshop, on a file under 4 Mb.

I run windows 7 64 bit, 7100, my bios and all my drivers are up to date. Kaspersky antivirus came with my mb, but never ran properly. I downloaded an update for windows 7, but still it caused windows to block it, saying there was an incompatible driver (?). I restored the system to before I installed it. That didn't help either.

intel core i7 920, 6 Gb ram, wacom intuous 3 tablet

help???

okay. how do i do that?

There's one .dmp file on my system, it was made at the right time to be for that blue screen. It's 311 MB. Hm.

wait, that was memory.dmp, i guess it's a system file... the minidump folder is empty... but i most definitely got that blue screen...

alright, if nobody has any thoughts, i'm going to go ahead and reinstall windows

Well, windows is reinstalled, and everything is updated again (the bios update should still be there, right?) but i have the same problem. just tested it with a 5 pixel brush - it lags half a second or so. maybe that doesn't seem like much, but it makes it hard to draw a precise line.

i just tested brushes in gimp and painter 11. they work fine. i had vista 64 on this machine before and didn't notice any problems with brushes in ps, but i switched os after a week (the machine is new) because it had crashed 4 times, once when nothing was open except a game of solitaire. maybe i just never tried brushes in ps before. 7 has crashed once so far, but it still seems more stable.

anyhow, the problem seems to be between photoshop and the rest of my machine. i guess i'll have to hope a patch comes out, and use painter and gimp for now.

btw, never found anything in the minidump. i opened it in explorer. could the file have been hidden? there doesn't seem to be a minidump folder now. Does windows create it when there is a crash? i guess i let that file get lost. well, maybe i'll be lucky enough to have a similar crash...