[reynolek]

I just had this issue -- I updated AVAST antivirus last night.

I put it in passive mode, restarted my machine and it was working again.

EDIT: After going passive, I could launch the game, but could not connect to any servers.

EDIT 2: Uninstalled AVAST as its not as awesome as it was in the past, and I finally have a concrete reason for removing it. Switching to Avira.