AVG Anti-virus had wrongly tagged Diabloii.exe as a trojan horse, making it a false positive. An AVG representative acknowledged the problem at the AVG official forum and reported this issue has been resolved in the latest AVG virus database update. If you accidentally approved AVG to delete the false infection, you will have to install Diabloii.exe again. If you have issues to play Diablo II, and you have AVG installed, you probably didn’t notice the trojan horse alert said it was Diabloii.exe. You may have to re-install the game, if you aren’t able to launch the game.
AVG: According to our database the false detection “Trojan horse BackDoor.Generic11.ATGA” was already fixed by latest virus database 270.13.112/2392 (released today at 9:31 AM CET). Please update AVG and check it again.