Television and Home Theater

I am unable to get the channel to change on my T.V. by the universal remote or by manually changing it with the channel up and down buttons located on the front of the T.V. The T.V. stays on a blue screen with the words "Video 2" being displayed. I am unable to watch my cable T.V. and at this time can ONLY play D.V.D's. Can you tell me what I need to do to correct this problem? Thank you.

All was fine until one day the picture and sound went out. Only a high pitched noise that can only be stopped by unpluging the power.

I have an RCA 50" DLP TV model # HDLP50W151. It is a little over a year old. While my son was watching it this morning it made a funny sound and the screen went black but the audio is still there. Does anybody have a clue to what might have happened.I appreciate your responses.