Avast is currently detecting some of the necessary WoW files as malware and is quarantining it so that the game can no longer connect. This is a false positive.
If you have Avast, you can configure it to allow you to login.
Q u o t e:
RIGHT Click your Avast task bar icon.
- click - "Open avast! user interface"
- click- on the right hand side "REAL-TIME SHIELDS"
the button on the LEFT of that page is; "EXPERT SETTINGS"
- click - the "EXPERT SETTINGS" button
a new little window opens
The list on the right hand side of that window has the 5th tab named; "Exclusions"
- click - "Exclusions"
- click - the "ADD" button
Into the little entry field that opens in that list copy/paste;
C:\ProgramData\Blizzard Entertainment\Battle.net\*
- click - "OK"
close your Avast windows.
(Copied from Slanderized's post)
