>I just noticed that the client uses the server to run a CCTV monitoring client software. Could this be a cause?
>Yau

Anything could be a cause.
Most respondents seem to agree that something is not right IN THE HARDWARE.
It is possible that the CCTV software is implicated, but I'd still suspect hardware (which would include network connctions end-to-end).

I'm also not so sure that Win 2K as server with workstations being WinXP might not be implicated myself. I'm too lazy to check, gut I seem to remember that there is something about this combination in the UT Bug List.

good luck