Hi KPaw,

Although I’m not the expert that some others are, it sounds to me like Avast is in conflict with some other piece of software on your system. Since you’ve spent so much time on the problem you’ve probably already tried this, but if not I would suggest the following procedure:

First, run the manufacturers’ uninstall tools of all security programs that have ever previously existed on the system. You mentioned Norton – theirs is here: http://us.norton.com/support/kb/web_view.jsp?wv_type=public_web&docurl=20080710133834EN&ln=en_US
Others may be found at the manufacturer’s website or at: http://thewebatom.net/uninstallers/security-software/

Then, uninstall Avast, boot to Safe Mode, run the Avast uninstall utility (http://www.avast.com/uninstall-utility), boot to regular mode, reinstall most recent version.

Then, if the problem persists, turn off half your autostarts (At a command prompt run msconfig and uncheck half the items under the Startup tab – leave Avast checked.), reboot, and see if the problem goes away. If not, re-enable those startups and uncheck the other half (excepting Avast), reboot. If you find the problem goes away when half the autostarts are unchecked, you know the problem is with one of those programs. Progressively re-enable half of those until you figure out where the conflict is.

Good luck!