Two PCs, starting to sound more like a AXBB issue - but that's a very very premature conclusion.

Can you post the results of "ipconfig" from a dos prompt? And are you familiar with Wireshark? - it would be useful to know if the comms to the board is bring routed onto the correct interface... but it's not something that you can pick up in 2 minutes.

I'm hesitant but thinking I could pull my UC300ETH so that you can test your PC against that as a known quantity - just for consistent comms.