Thanks for your help everyone, finally figured it. It was me being really stupid - i assumed the serial cable that comes with the empeg is wired straight through. It isnt, and i hadnt tried connecting straight out of the sled into my PC - that worked fine. Also the sled was wired correctly to start with, which means the FAQ wiring diagram for sled pins 8 & 9 is wrong.

Thanks again for your help. Looks like ill have to go buy a null modem cable tomorrow, but at last my docking unit is finished!