Help, please
I had the same "unknown error" message and chose the repair function as described above. Restarted the computer. Then found I had to get a new registration key, received that, entered it - initial check seemed to go OK, BUT resident detection is still shown as disabled, and the computer makes strange noises if I try to toggle it on or do a scan. It seems that whatever was fundamentally wrong has not been repaired. Am I going to have to uninstall and reinstall all over again? If so, will the registration key I received just now still work? Does all this mean something is seriously wrong and my copy of Avast has been disabled by some attacking agent?