I'm having this problem as well. Except I can't even run the Blizzard update for StarCraft 2 because avast! quarantines it before it even runs. I'm pretty sure nothing is latching on to the download, as it's directly from Battle.net...
Agreed with above poster. An ETA on this being resolved would be greatly appreciated. I can't play my game until it is.
Also, system info if it helps:
Windows 7 Home Edition, 32-bit
avast! Free Antivirus -> Status: Secured and up-to-date, silent gaming mode
Windows Firewall: ON