I'm not the most pc savvy but it sounds like you've tried most of the things I would have already.
Clutching at straws, but until one of the resident gurus comes along to suggest something better, a couple of things you could always try:
- check that you can still post with the 560 back in your pc (to rule out the motherboard)
- try taking out your RAM and sticking it back in or using alternate slots....or possibly even running with a single stick (oddly enough I've heard of one person who claimed they got a red vga led due to their RAM not being seated properly)
- try a different video cable and if possible a different video out on the card (e.g. dvi rather than hdmi) to rule out a problem with a particular port
I'm not 100% sure when the led is meant to come on though so some of the above suggestions may not be particularly valid
Good luck!