Is this run through logon scripts.

We have ocasional similar problems with these. If you have a PDC and BDC or two domain contollers have you copied the scripts onto both DCs. This is not always automatic.

Do you have roaming profiles, could be a bandwidth issue, although I'm speculating.

If its standard profiles, could be that you have bandwidth issues generally, or that you've got other connection problems. We have experience issues with XP connecting to shared folders.

Best thing to do is to carry out ping tests to check bandwidth unless immediately you can eliminate this. Then check out the event viewer on the server and post any errors.

We run on a similar system so if you let me know your profile setup, I may be able to help