I had a similar problem with my Windows XP Pro setup but it turned out to be because the unit was plugged into the same USB device as my ADSL Modem. If you want to use USB then make sure that the unit is plugged in to a USB device on its own just in case it's a power drain problem. I used the USB connection to program my unit with Emplode to have a fixed IP (I used 10.1.1.69 with a subnet of 255.255.255.0). Then you should be able to easily connect the unit to a switching 10/100 hub like I did or a 10base-T one will do as well. A dedicated 100-baseT hub will NOT work as the NIC in the unit is 10Base-T.

Finally, don't do what I did and fear the worst. It'll be a simple problem whatever it is and with the help of this forum you'll solve it soon enough, I'm sure!