If your antivirus software detects a virus in a Blizzard game folder, the detection will most likely be a false positive.
Failed to download files from Blizzard servers.
Failed to download files from Battle.net -- "We're having some trouble transferring data. Please wait while we keep trying."
How to resolve this issue when installing or updating a game
What to do when getting an error that the Battle.net Account has logged in somewhere else.
Types of issues Blizzard Customer Support can help you with on Activision games
Information about how to copy a Diablo III console save to a new game or console.