what games? Could you be more specific?
Most of the problems with online games is caused by behavioral shield checking the behaviour of the programs but sometimes it influences the program run and some of antichating rootkits fails because of that. In most of the times it should be enough to switch of the BS when you want to play the game.
We are removing all the known incompatibilities / problems continuously. however it's difficult if we don't know what programs the avast! interferes with...