I'm obviously missing something here. We've tried with a 3COM 5-port switch and with a DLink mini-switch and have the same problem. We've already turned off port security. The problem is that the port seems to only support 3 devices on the mini-switch. How can we get all 5 ports to work?
Sounds like the 3750 is restricting how many mac addresses per port are allowed. May have to post a scrubbed config so that we could look at it.