Is there such a thing as your antivirus software becoming corrupted and howd you know if its happene

Probably. If you get error messages from the antivirus software then something is probably wrong. Someone might have been up to no good, but it's also possible for part of the hard drive to go bad, and the antivirus software may be stored in that area.

If the antivirus software won't run, try booting from something like an antivirus recovery disc (perhaps the Norton Internet Security CD, for example), and if nothing seems to be wrong after a scan for viruses, try re-installing the antivirus program.

And it probably wouldn't hurt to use a disk-scanning utility to make sure there are no corrupt sectors or clusters on the hard drive. A quick scan would be better than nothing, but a surface scan would be even better, but it may take a very long time.

I'm more familiar with Norton Systemworks than I am the other utility suites, but it seems reasonable that there are other good programs out there.

Good luck.