Are you running Windows 2000 or Windows XP?
If so, disable the "Windows Time" local service.
I remember thinking a lot of computers I worked on here at college were screwed up, but they were all just running the Windows Time service, the servers or domain controllers must have always been behind by 5 minutes. I remember trying to compensate with a time synchronization program LOL, it just made it seem crazier.
XP has built in SNMP/Time Protocol syncing to various internet servers but I haven't played around with it much.
Anyways I'm just running with Windows Time service disabled and a time synchronization program now that syncs to the US Naval Observatory (tock.usno.navy.mil is my preferred time keeper in case you're wondering).