Vlk
17
Of course it’s a problem in the avast installer, but it’s hard to tell who’s guilty. It seems that the SP2 setup somehow screws this key… 
A work around is indeed to patch the registry key in regedit – or use the reg file supplied in this thread: http://forum.avast.com/index.php?board=2;action=display;threadid=6991;start=0#lastPost
Cheers
Vlk