I've seen this same problem too, on multiple computers.
One recent, about a week ago, was an eMachines 2GHz system with XP Home installed. I had uninstalled McAfee since it was already past its "free" working year. After installing version 4.6.652, I'd shutdown the computer and I'd get that Access Violation error box. I've seen it more than once on the same system. And the system hadn't been on too long for each boot, since I was updating the system, removing adware, and installing anti-ad programs.
I just hope since I had given the computer back to the original owner he doesn't call me back with questions about the the shutdown issue.