While it may be the TV, try connecting the cable box back to the HPT5064 and calling your service provider to reset or refresh the cable box while you're on the phone. Often times, HDCP (content protection) is also a symptom of the box not recognizing that the TV is an approved device, and a reset or update of the cable/sat box's firmware will often times fix that.
It's free and worth a try. Keep me posted.
A couple of days ago my samsung 50" plasma hpt5064 tv stopped displaying anything on the screen. The screen is black but sound still comes through. I cant get any menus or anything to show up on the screen. I hooked up my cable box to a different tv (same exact set up) and it works fine. I know this issue is with the tv itself but I dont know what the problem is and if it can be fixed? Ive noticed this is a common problem among samsung tv's while doing some research online but have yet to find a solution. Please help.