Try the cable on another machine, or get another xbox to try. if the cable is faulty which i doubt it is. it has a 1yr warranty. so yes, Ive heard of people trying to change the HD settings ie 480 720 on xbox dashboard. memorise the control to change settings even when you cant see it on screen, it may come on. starnge how your having the same problems as me, but mine was blown i think when i touched the component leads on the speaker outputs from my AV amp. but maybe the xbox was faulty from manufacture. When on VGA mine came on, and was all red no green colour at all. composite worked fine for me, but crap picture.
dont send anything back, until you have tested and eliminated everything.
regards
Burnie
lol, Oh and i mean dont send anything back to MS. not dont reply on here.
good luck
Burnie