Syncing with Internet Timeserver results in a time that's off by 45-100 seconds. ???

[Jeff7]

I don't know what's going on here. My Date and Time Properties has the Internet Time tab, and I've tried synchronizing with some of NIST's servers at time.nist.gov, time-a.nist.gov, and nist1-chi.ustiming.org. Windows reports that "the time has been successfully synchronized, etc etc." All servers give the same result: The computer's clock immediately differs from what's found at Time.gov and Greenwichmeantime.com, from anywhere between 45 and 100 seconds.
Is this something messed up with my motherboard, or is it the OS? How is it happening that it reports a successful sync, and yet it evidently didn't? I'm hesitant to believe that the atomic timeservers are off.