Problem with Windows Online games - zclientm.exe

Hi!
I recently installed McAfee ViruScan Entreprise Edition and a wi-fi routing
system which works just fine. The only thing: I cannot play Windows online
games anymore! The game (ex : backgammon) opens, I get the usual starting
windows, up to the game board. Even the dices roll after the starting throw,
and that's when I get the error message that zclientm.exe could not start
etc. etc.

Anyone got a clue?

Thanks!