After todays update its back! Figured I'd do a google search just to be safe and I came across this thread (amongst others).
My game was updating then it fired up a warning of a Trojan.gen if i recall. Managed to exclude it in the On Access Scanner and Avast itself so it doesnt bother me, but it's still abit irritating.
I'd been playing the game perfectly fine a few days ago with no bother, and Avast seems to update daily so its obviously been introduced accidentally again?