Hi. I'm experiencing some problems with photoshop, I'm working on a file, and suddenly it crashes. It usually crashes when painting. It doesn't vanish, it just stops responding. The resolution doesn't seem to matter, it does it with 500 x 500 pixel images to 3000 x 3000, but the higher the resolution the more likely it seems to crash. The thing is, I open the same images in Painter, and everything works just fine.
I searched for photoshop crashes in google, and I renamed the MMXCore file in the extensions folder to MMXCore.old, and that made things run smoothly... for a few minutes... then it crashed again.
I don't think its a hardware problem, the computer is fairly new.
Any ideas?

EDIT: The crashes are freezes. Sometimes photoshop freezes and stops responding, but other times it freezes and then continues to function normally. I'm thinking this may be a memory problem, but I don't have other programs open. I thought it was because I had painter open at the same time, but I closed it and it still happens.