No picture, can't set inputs on TV

My Dynex 20'' LCD TV/DVD combo was working fine until i got HD service, connecting to DISH satellite with HDMI cable. i immediately had trouble turning it on -- it required two clicks of the remote -- and it sounded like it was trying to turn on the DVD player. A month later I got no sound. But I could fix by jiggling the HDMI cable. For some reason it would never stay on the HDMI input. Now I can't get a picture. When i turn the set on, it briefly flashes an input option -- AV1, component, etc. -- then immediately goes black. If i put in a DVD, I'll get sound but no picture. The unit is 14 months old. Is this a back light issue? Any advice would be much appreciated.