Element hdtv flx3210 shuts video off after a few... I purchased the Element hdtv model flx3210 in

Question

I purchased the Element hdtv model flx3210 in novembers black friday sale from circuit city and the tv sat inside its box for several months. Today my wife at last sold the old CRT tv set and we un-boxed the new Element hdtv and we watched it in happiness for all of five minutes with video/audio signal being fed by regular cable via 75 ohm scrwon connector. Anywho after five minutes the screen shuts off and the audio is still heard and we pressed buttons to change channel and the audio changes but still no video. The button on the front stays blue.(the one that turns red when you shut the tv off). On the rear of the 32 inch Element hdtv we noticed a blinking red led goes on as soon as the picture from the front cuts off. What to do since the tv is brand new and we never tested it to see if it worked since we had extra CRT tvs around the house.