I haven't experienced it because I don't run W2K here

, but in general, W2K is quite paranoid about maintaining time sync for both security and data integrity reasons.
As a good starting place, check to make sure that either 1) your e-smith box is a lower-stratum time server (this should be the default, anyway, as far as I'm concerned), or 2) that NTP (port 123) is allowed to pass through the gateway and any other firewall in the path.
My guess is that either will fix this, although the first is preferable, as it makes the SME box itself a good master clock for the rest of your network, and you'll know its clock is always right, too.