Logon XP workstation to W2K server AD

I have a W2K server w/AD and all workstaions have WinXP installed. I have some workstation having problems logging on. The problem is that I have created sricpt for each user to network a public share and a user share on the server during their logon as a drive letter. Most users are working fine, but some have started not getting their network share to show up in MyComputer and they can not access them. I can go to a different workstation and log them on and it works. What is causing this and how can I fix it?