Same thing with me!! Ive had this tv 2years.. i was sent out a replacement for the previous one the year b/f.. that one was giving me trouble also.. the warranty has expired on this one.. i purchase from hsn also.. this tv is ****.. it can't even be fixed in a tv relpair shop!!

I've had the same problem. Usually, if I turn the TV off and then back on again, it's fine.

If you get some pictures the problem is most likely a bad tuner, as when directly connected a video source to the RF (Cable Coax) connector.
Try using an s-video cord instead.
If you never get any picturethe problem is related to the power supply, more precisely, the SMPS output is just a bit high causing the microprocessor to go into protection mode cutting off the horizontal oscillation, but as sound has a different power source from the SMPS, it will work without any problem. You will have to get to a qualified sercive engineer to fix this problem.