I just installed Comodo Antivirus (Beta 18.104.22.168) on Windows XP sp2 and the reboot after the installation ended in a blue-screen and automatic reboot. This continued until I booted with the “last known working configuration” (using F8 during boot). After that Windows successfully booted, but the on-access scanner of Comodo Antivirus failed to load. All other features seem to work fine, though. So I assume this is a bug in your on-access driver.