[The_Psy]

mmm... stutter is a kind of lag... and Frustration is not that wrong, it could come from the cpu or the graphic card who is overheating. Did you try to leave your tower open to check if it go better like this? Do you have enough free space on your hard drive? Is your swap drive not full? Does it apper all the time or only when you have a big number of planes or objetcs in the mission?