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>Hmm, those switches look like enterprise class devices with a great deal of managed configurability. Very powerful, but lots of chances to make a misconfiguration, too :-/
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>I'd check the simple stuff - when testing with just one switch, try different patch cables at the router(s), in case there's a bad one. It might not be a bad idea to try different patch cables at the workstations, too - a bad cable there might be just barely OK/in spec for one of the switches, but not for the other. See if you can round up some good Cat6 patch cables for testing. Yet another thing to try would be plugging in one or both of the computers to different wall jacks, in case there's bad wiring somewhere.
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>Expanding on Hilmar's idea about different ports - try to find out if the ports being tested are on the same network segment, or if the switch has been segmented and you're trying to communicate across segments. If the latter, you may find the traffic is being routed circuitously via some strange path/route on the rest of the network, leading to delays.
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>It might be worth pointing out to the engineer that VFP apps utilizing VFP data tables require complete, properly configured SMB/CIFS support - think Microsoft enterprise-class networking. If the network supports primarily non-Microsoft networking, the engineer may not be too familiar with what's needed to make a reliable network for VFP.

I will relay the information to the network engineer. However, I am reluctant to ask for every possible test as they (the IT department) is already start to think that the problem is simply with VFP (even though I have the same application running at about 50 other companies). I am sure you know that VFP is not the most popular with some ITs these days. The network engineer I communicate with (over email) seem to be really trying to help but I don't want to wear out his willingness. So, what I am saying, I have to ask him to try things that are being of high probability to hit the problem.

I believe that cables is not the problem. You see, he tested this problem on 4 different computers in different areas of the company. There must be different cables and different wall jacks involved. And he said that the problem is always when 2 computers are using the same switch. That is, when 2 computers loading the application but using 2 different switches, no problem.

He also mentioned the following:
"I also ruled out that it’s an issue with two users on the same VLAN, I moved myself off of the same VLAN that Niall was on and that didn’t help matters". I don't know what VLAN means though.

I believe your point about the network segment might be helpful to troubleshoot this problem. I will pass the information to the network engineer. And also the SMB/CIFS support, which is also way over my head :).

Thank you very much for your help.