Can't be McAfee as mookdog uses something different and had the same thing happen. <snip>
Yes, it can be.  If it is as poorly implemented as McAfee, it certainly can cause these types of problems.  Making a computer unstable is a trademark of McAfee and Norton.  There are probably others that are just as bad as those two are.  Because of the way the install (over-writting system files) you really cannot disable them entirely.
Anti-virus programs do bad things to Aces High because we are constantly updating config files.