that darned 0xc0000005 error

hey ive seen this error before, at least im sure i have...."The application failed to initialize properly(0xc0000005)blah blah, then pc crashes without saving settings. Sometimes it crashes without the error.
im workin on my friends computer, so of course im trying to fix this as soon as possible. he had no virus protection or any thing, so of course thats where i started, i ran spy bot, threw avast on there, and found several things that i of course deleted. it happened again!!(though not as regularily.
also he is running two different users on his machine, and only filled me in moments ago that the other user has never had this happen....only his user acc. cxould there be a quick fix to this, or does he maybie have to delete that user and start anew? he says it seemed to happen around when the new user acc. was created?
any ideas??......
this just in... LSASS attack was just picked up by Avast.... any help please