Slow Access 97 response

I have a small Windows NT 4.0 network where 6 users are using Access97 databases that reside on the server. The 6 users are all running Access 97 on their own PC and all are setup the same. This setup has been working fine for over a year now. @ weeks ago, 2 of the users started having very slow response to opening and using any of the Access 97 databases, the other 4 users have no problem. Nothing has changed on the PC’s or the network. I have compacted the databases, repaired the databases, checked the network connections, defragmented the hard disks, and increased the paging file size to no help. Any suggestions on where to look next would be appreciated. Thanks.