I know that this doesn't help much be we run an installation of about 18 users on WinNT/2000 against P4D running on NT and we don't have any problems at all. It sounds like you've got a network problem. We used to run VSS.

The biggest issues that we've run into are the lack of a 'p4 rename' command and no VSS-style "links". I know that a 'rename' can be done with integrate/delete but it would alleviate a good deal of support headaches for Perforce admins if Perforce would add a 'rename' command. Users to don't know about the integrate/delete trick usually do an add/delete which causes history information to be lost.