I can't activate the antivirus anymore

After installing the Windows service pack 2 SP2
i can’t have access to the antivirus anymore
Cannot find the file. Error (a setiface error has occured 2 Try to re-install or contact…
I tried to removed it impossible do not find the file (but still see it on my computer) I tried to re-install it…nothing same problem
What do to ?

Are you by any chance also using SpySweeper?

Can you try to repair your installation?
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove
Then choose Repair function in the popup window (Repair).
You must be connected to the internet while repairing.

If this does not help, can you uninstall / boot / install / boot again?