GameSpot is reporting that a large number of PC games are adversely affected by Microsoft's newly released Service Pack 2 for Windows XP. Some games, like Star Wars: KotOR and Warcraft III simply have multiplayer problems with the built-in firewall software. Other games, like Freedom Force, may not function at all.
You'll also want to check out Microsoft's full list to see if any of your other favorite programs are affected before installing the service pack.