Hi,
I have the same problem, after replacing Norton Antivirus with Avast 4 Home. It doesn't show the avst icon in the system tray.
Looking forward to a solution to this......
Oooohhh, noooooo.... Norton again!!! Get away from it!!! Do not install more than one antivirus program (resident). Norton is the monster of the monsters... Never gets out of the registry... unless a lot of work can be done... But be happy, I´m here because I get rid from Norton, after Vlk and Kubecj precious help, lot of lost hours... But I´m here, I´m avast! To get rid from Norton is one of the most difficult things in the earth!
The main reason installation fails or systems freeze when using new AV programs is the inablility of the old ones to uninstall properly. I have had to dig up removal tools for Norton before anything would operate properly. This is not an avast issue, Kaspersky, McAfee and even Grisoft (e-mail plugin) have their own unique uninstall issues as well.
Take a deep breath and go to the
Norton desinstalation sage!.

Wellcome to avast both of you

Rexcard, I used AVG anti-virus and replaced it with Avast like you. Maybe you have to clean your registry and do a reinstallation of avast. But, first, answer Vlk...