Just a note: I'm running Windows Xp Pro (2600.xpsp2.030516-0318) and I've seen similar problems. But then, this is an a-typical system (that is, I threw out all the useless junk Microsft packaged with it, stealthed and hardened the ports, shut down un-nessesary services, etc.) so it's not surprising that this configuration wasn't tested during the Beta cycles.
That is all.