Xbox 360 No Video

I was downloading a game and suddenly my Xbox 360 was hard rebooted. After that all the rings glow green and audio works, but no video. Can't figure out how to fix this problem because due to video failure I can't see what Xbox 360 is doing. I have looked all over the internet for the solution but can't find any help. Does anyone know how to solve this problem? BTW my Xbox 360 only a few months old; I got it from Walmart through http://www.dealrocker.com discount deal.

I appreciate any assistance you experts can provide.