can someone help me with this? I searched through the FAQ's but didn't find a similar problem.

program used: PS7
problem: error message titled, "Could not complete your request because of a program error" appears whenever I try to use a brush/eraser/clone stamp/etc on something. everything else works.
solutions tried: closing all other windows. closing PS and restarting it. restarting the computer. cleaning hard disk (deleted several huge media files). defragged the files.

nothing seems to be working. sometimes it randomly starts to work, then it flashes me the error message again. someone please help me before I burn my own brain.