Alas, this upgrade went no better than v6 to v7 in February. At 1st I thought I was home free. The upgrade via the GUI went okay, and showed the new version number on the summary screen. But it never asked for a reboot. That made me suspect something was wrong. I rebooted, windows started fine, I logged on fine, and the system hung. Rebooted again, same thing. Rebooted into safe mode, uninstalled avast and rebooted, ran the uninstall tool and rebooted, ran Ccleaner, and then ran clean install of new version. Then my firewall began to act squirrely, like it did after the upgrade from v6. Another reboot, and it looked like it was all good. I ran a quick scan, during which none of my programs would respond. After the scan, I rebooted again. We'll see how things shake out the next few days.
Update: Twice today my system froze during (2) different processes. 1, this morning as I was running a System Explorer scan, it froze in the middle of the scan and locked the system, forcing a reboot. 2, system locked again tonite while Winpatrol was verifying my Startup list and scheduled tasks, which was odd because everything it kept throwing on the screen had already been set months ago, except for avast emergency update. The error message on the screen before being forced to reboot was that my firewall closed in an unexpected manner. When I go to Admin Tools and click on System event viewer log it says it is corrupt and cannot open.
Update: Switched to AVG, Sunday, after 3 days of system lock ups, unresponsive programs, etc. Call it a crisis of confidence.
AMD Athlon 3000+ 2.17 GHz, 1.50Gb ram, xp sp3, avast 7.0.1451 free, Privatefirewall7, Mbam free, SaS free, Winpatrol.