Losing Roaming Profiles

Hi.There must be someone who can help regarding the problem that I have been having with roaming profiles. We have some user defined logon’s that should enable that person to log in with there profile(MY documents, desktop properties, etc) and get access to certain network drives. But what happens with couple of log on’s is that the profile won’t appear. Rest of the logon profiles work ok. The server with the profiles is Windows 2000 Advanced server and the client desktops are a mix of Windows 2000 pro and NT4.

Someone pls help.

Thanks
Dave