I've run into what sounds like the same issue a handful of times with some (but not all) PDS Ethernet cards I've tried. What ended up yielding success was using a router or switch with manually configurable ports, or using bridged networking on a Mac or PC. The trick was to set the port on the switch, router, or modern computer to 10Base-T rather than auto negotiation. Sometimes this also disables Auto MDI-X and may necessitate use of a crossover cable if connected between computers. Apparently some of the cards I own respond incorrectly to auto negotiation from a modern device, causing it to select an incompatible mode. I did experience brief success intermittently before changing the port setting, but rebooting or disconnectong anything would send me back to frustration. I attributed this to just be a fluke where the PDS card didn't "confuse" the modern device. Hope this gets you going. I can't remember if half vs full duplex makes a difference. Someone also suggested putting a 10Base-T hub or switch between the PDS card and router. Didn't have one to try.