Disappearing profile files!

I’ve just got a new job, and my first problem with the network is as follows – now’s probably a good time to earn some brownie points, so help me out!

We run an NT4 domain, with win 95,98 and 2000 clients. Now, for some reason, every now and again, the users files (stored with the profile in a home directory) disappear inexplicably. This has only happened to users that have moved from regularly using the same win95/98 box to a 2000 one, which leads me to believe it’s some difference in the way they deal with profiles/home dirs. Any suggestions?