I think McAfee is inteferring with some of my games following an Security Center update. The version is 10.5.
Following the update, the game, Europa Universalis III, slowed to a crawl. Before the update it played fine.
Does the Secuirty Center still detect games?
Scan not happening when the game is on? This automatically should not happen but worth a look. Open the task manager ie ctl+alt+del keys and see when this slowing happens what is using the cpu cycles.