avast error message during changing configuration

Hi

I’ bought avast 4 pro edition but when I try to update the software I have the following message:there was an error in the changing of product configurations.
what’s going on?
what I have to do?

thanks

Can you try an installation from the scratch?
Or, first, try to repair your installation (through Control Panel > Add/Remove > avast > Uninstall > Repair).