There are a couple of things that could cause this, unfortunately there is no reset for this television other than unplugging it. It will have an internal failure at this point. I will try to explain the possibilities the best I can.
First there is an AC fuse in the tv, however if there were no storms or power issues, this would be very unlikely. If this were the problem it would be best case scenario, normally this runs around $100 to have a tech come to your home and replace. If you can use a meter we can check and replace this very cheap.
Next, you could have a failure in the power supply, we have seen some capacitors fail in your model and cause funky problems like this. If this is the case you could be looking at somewhere around $125-$150 to fix the set. IF the power supply had to be replaced you could be looking at $150-200
Last could be the main board, this would not be good news because you could be looking at $200-$300 for the repair.
Either of these could cause your problem, but it will require troubleshooting to determine the exact cause of your problem. If you have experience, and test equipment and would like to attempt some troubleshooting I will be happy to assist you, however if you do not have equipment or experience then you would need a repairman at this time to get an exact diagnosis. I am sorry that I don't have a quick fix or easy answer for you on this one, it is definitely an internal failure.
Please rate my service and push the submit button. If you need anything further at all, please use the REPLY TO EXPERT tab and I will be more than happy to help you further.