This is just a remake of my original post that detailed a bug in 5.1.889 + another odd one I noticed. These aren’t particularly “program-breaking” but are important for polish nonetheless. The original post with all the information regarding the blank scanning logs is listed here: http://forum.avast.com/index.php?topic=69418.0
The only additional information I can provide is it still happens after doing a program update from 5.1.889 to 6.0.1000 and that this also happens on Windows XP (also did a program update from 5.1.889 to 6.0.1000). Note: the missing right-click context menu scan option for the downloads folder is fixed (so disregard that in the old link).
The second bug relating to double update reboots concerns using the built-in program update tool from 5.1.889 to 6.0.1000. Everything went smoothly until I did another program update check after rebooting the 1st time (when the update finished/prompted me to). While the updater said the program was already up to date, a window popped up again anyway saying that a new update installed and that I had to reboot. I figured I’d say yes just to be 100% sure, and after doing the 2nd reboot any subsequent program update checks did not trigger this.