Dave,
You would have to get a TS and licenses for everyone to use RDC. You can't run multiple staff off the server.
Go to Amazing Utilities, Advanced Options, Test speed to and from databases just for fun.
Also, make sure you NIC card in devices is set to auto-negotiation. Also, rather than test using RDC which isn't helpful at all, connect one computer to the server through a small switch and see what the speeds are. If it's fast like two seconds, put it back where it was. If it is slow, you have the answer.
Just by connecting to the server directly and it is a lot faster, you just made your switch a possible candidate. You could then use the 4 port GB switch that you know is good and run the server cable and three computers through it and see what you get. Generally wired would be faster than wireless, so that should tell you there is a bottleneck somewhere. I would definitely look at the switch.
