Generally speking, repairing avast installation could solve this:
Control Panel > Add/Remove programs > Change/Modify > Repair option
or
Control Panel > Add/Remove programs > Uninstall
Boot
Install
Boot
You can take a look here for a full description of the settings:
http://forum.avast.com/index.php?action=display;board=2;threadid=1647
See ResidentBalloonShown=1 value 