I found that recently when playing Call of Duty or MoHAA Breakthrough, the games would stutter and be herky-jerky. It was both online and single player, so I ruled out any network issues. I ran Activity Monitor and found that Virex was running a bacxkground scanning app. I had recently upgraded to Virex 7.5 (a perk of dot-mac) and was unaware that it had this activated by default. Once I turned off the background scan, everything worked fine. I'm on a 1.8 single G5 with a gig of ram so both games run fantastic. If anybody else is experiencing issues with games, or other apps, running funky after ugrading to Virex, you might find this useful.