IS My AV cable broken or is my Xbox 360?

here's my problem: one night I was playing halo and i decided it was time to go to bed. I shutoff my Xbox, moved it into my room and turned it on. No picture. I checked the channel and it was ok everything was hooked up correctly so i decided to check on our living room TV. still no picture. when i was playing halo there was no visual disturbances or problems. I do have audio though. just no video. when i set it up i have the default blue screen of our TV but I hear the 360 startup noise. I'm really hoping it's the AV cord, not the 360. oh and there is no red ring what so ever its all green. Any Idea's?