I don't know where to do this in NT (I'm more of a Netware rat), but I would watch the files being opened by the workstations by monitoring network activity of the user logged in at that workstation. If you're opening the files programmatically (rather than as a part of the data environment), place a WAIT WINDOW after loading each table, so you have a chance to see the files being loaded from the network server console one group at a time.

It would be interesting to see if it's related to the number of files being opened at that workstation, or whether the OS is giving up after requesting a file be opened. I don't recall what you said the workstation was running (NT? 95? 98?) but if there's a setting to increase the network timeout (a setting at the workstation), I'd try tripling that for testing purposes.

Hope this didn't ramble too much - just stream of consciousness this morning...