Do you have access to a multimeter? You could measure the voltage between the alt 5v solder point and the metal shielding of the case. Should be 5v. You can then with the chip installed also measure the voltage between the top of pin 6 on the back of the chip to the edge of the case, should again be 5v. Although you removed pin 6 from the pinheader, the alt 5v trace on the chip's circuit board is common with pin 6 in the socket. (1.0 to 1.5 boxes have 5v here, why they don't need the extra wire.) If you have 5v at both of those points then the problem lies in the connectors to the switch bank, the switches themselves, on the chip circuitry or a bad ground.
Also if you have a multimeter you should be able to test the functionality of the switch bank as well.
Once you do get your chip powered I'm pretty sure that you will not be to see FlashBIOS using component cables though, not sure if S-Vid is supported either. The FlashBIOS video support is pretty minimal. You can still work around this a few ways. If you have your Xbox on a network with a router, maybe the router will report what DHCP address the Xbox has picked up? If so you can then use that IP and do the HTTP flash method from your computer. You'll be partially blind to the status I think, but is should work. Other solutions would be to use another Xbox to set up the chip, then transfer it to your box. You'll obviously need to get D0 sorted out on the alternate box, although in a pinch you could manually ground the point directly from the motherboard in order for the chip to boot. Final solution would be to use a programmer.
-Whoopin'
