Vista clock time skewed

I have two office PC's running on my desk. One running WinXP Pro, and the
second running Vista Business. The two machines are logged onto the company
domain server. Here is the issue...
The clock on the WinXP machine is correct, however, the clock on the Vista
machine is always 5 minutes too fast. If I logout from the domain and logon
to the local account, then the clock time on the vista machine is correct. I
have tried stopping and restarting the net time service, this has made no
difference. Any ideas how to solve this silly problem?
Mark V.