>>Is your NT server set up with a proxy server (e.g. WinGate) so that all LAN users can access the Internet through its (shared) modem? If so, there typically is a setting in the proxy server that tells it not to act as a proxy for addresses on the local subnet. If this has NOT been set, the proxy server will slow down local traffic by acting as a proxy for all local LAN communications over TCP/IP.
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>The LAN has no proxy server, pretty much it is a straight NT 4.0 server with 4 workstations attached via a hub.
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>John Brooks

Hmmm... you may have already tried this, but I'll mention it anyways... have you confirmed the problem occurs with ANY 2 workstations as opposed to ANY 1? That is, if you ran the test with PC #1 and added PC #2, you then tested with PC #3 and added PC #4 (etc. etc.) Also SWITCH OFF any workstations not directly involved in the testing.

You could also try running the second instance of the program on the server console, or as another instance on a workstation.

I would hate to think that a jabbering network card in 1 PC was causing all this.