Well, I don't have any knowledge of the card and the link to the loopback cable is broken, so here's some general musings that you may have already tried.
Check Device Manager in Windows Computer Management for problems in the Ports section.
Launch two instances of Hyperterminal, each attached to a different Com Port, and use a null modem cable to connect the two Com Ports. Try setting both Hyperterminals for no flow control.
With no flow control, your null modem cable can consist of TXD crossed to RXD and ground connected through, three wires. If you haven't discovered them, RJ45 adaptors are the world's coolest cable building invention ever - Link provided for picture only, not site endorsement: http://www.pccables.com/01910.htm
. Available in DB9, DB25,male & female. (Get a de-pinning tool, too)
Does your computer have a built-in Com Port. Involve it in the test.
As above but use two computers, if you've got them.
Reinstall Windows. (Just kidding!)