EDIT: I solved the problem miself. It's very easy: Shutdown your Mac and reboot in Safe Mode (hold shift after the boot sound appears) and delete the Avast.app
I was using the Mac Beta of Avast on OSX 10.7.3.
Since i've updated Avast to version 7, it doesn't work anymore.
Thats what it looks like: 
Restarting the Mac doesn't help.
Also there's no Virus on my Mac (scanned with ClamXav)
If i'm trying to uninstall Avast by clicking "Uninstall Avast!" in the menu bar, nothing happens.
I hope you can help me to uninstall it, because I would really like to use Avast! in the future.
