The link light 'error' in Windows is exactly fitting in the NWAY problem. The card autonegotiates a speed with the router - in this case, 100BaseT. Both the router and the card then try to configure themselves for communications at the negotiated speed. The router succeeds and sets itself for 100 mode; however the driver for the card fails, due to the hardware bit error. The card drivers set 10BaseT half duplex - which is what the bit error ends up with - and wham! No communications. The card and router are on different wavelengths.
If you can, please pull the card again and search the board for a FCC number, and post it to me. We will have to do a FCC cross-reference lookup, based upon the card's FCC authorization number, to find the manufacturer (all computer electronics in America are approved by the Federal Communications Commission for a class, A or B, which depends upon how much RF radiation it emits and how much it causes, or receives, RF radio interference. They keep records of their approval codes). Hopefully that info will get us new drivers - to get 100BaseT this is the only solution. The NIC's speed is a combination of hardware and software - the hardware chip in the NIC negoiates a speed with the other connection that it believes it can sustain, gives that info to the driver, the driver sets itself and the card for that speed, and communications begin. The hardware handshaking bit error in the 21143 doesn't allow the chip to handshake, and report to the driver, the correct speeds.
Since the driver's options do not allow manually disabling NWAY independent of the Media Autodetect (and 100BaseT not full duplex set on both cards manually doesn't work (you tried?) which is fitting in the error reports, still because of the dual-mode set bit error) an updated driver is our *only* option.
Part of the problem is the router - it is a smart device, not like a simple hub. The router needs to negoiate its own speeds.
Either we find a newer driver with the correct patch or stay in 10BaseT mode all day. :-( Your mileage may vary...