win 98- win 2K disconecting drives

I'm experiencing the same problem. REncently we change our
server from novell to windows 2000 the most of the
workstation are running windows 98 and windows 95.

In some cases, when user leave alone the machine for some
time, when he goes back he can't access his network mapped
drives, because the access is denied. When I check the
user at the server in the active directory client, it
appears locked, so what I do is unlock their account, then
go to the workstation and disconnect the drives and then
reconnect.

We connect to the server with windows networks service,
and we don't specify and IP address, or DNS. So we choose
the automatic optian IP address options.

If you have any idea, i will really appreciat it.