I have found that Automatic Windows Updates appear to disable SystemGuard Protection. Twice now I have noticed that when Windows updates have finished downloading and updates are installed, SystemGuard is disabled and not re-enabled after Windows Update has completed. Perhaps this is a Microsoft-McAfee conflict issue?
It isn't just McAfee that's effected either - I've found that Microsoft's Malicious Software Removal tool incorrectly identified another application as a trojan in Vista, also a self-update disabled another A/V that I have installed in Windows 7 beta.
Ex_Brit, I have to ask you this question. McAfee is obviously a mult-million dollar company with I assume more than one techical person on staff. This problem has been going on for over a year now. McAfee has even lost some loyal customers because of it. Why, in the name of Bill Gates, can't McAfee hire some geek to fix this once and for all? You have to admit, this makes McAfee look really bad.