Worst one I've seen so far is with Operation Flashpoint played multiplayer over LAN. If you have machines running both XP and 98, the OS type not running the server will dump out of the game after a period of time. It's very frustrating if you've laid heaps of mines, taken out 5 Tanks and are sitting in a nice sniper location(SVD Dragonov rocks) waiting for the enemy troops to arrive and the game suddenly quits.

I don't use Windows XP because dual boot 98SE and Win2k works perfectly for me.