As far as I know avast! has a special Instant Messaging Shield - the Shield is protecting the Messaging programs and there is no need to set MSN Messinger, the shield is protecting it automatically
Just ensure that you have turned ON the IM Shield
I replaced in options ccIMScan.exe (norton) by ashquick.exe (Avast)
Tested en it works good
Poster .M:A:S:. Also thanks
I have turned ON the IM Shield alrady and it works
Only if somebody send me a mp3 or other file than after acception
MNS was asking for a viruscan and did not find the file