My UN46C8000 has started clicking and blacking out. The "Samsung" remains lit but the power switch does not function. After 10-15 minutes it might come back on at which point it can be turned off. Other times the power has to be disconnected for several minutes before it will "behave".
This TV replaced another Samsung that exhibited the same problem that then progressed to the point that you are experiencing. I tried to give it away to any one who would take it for just the cost of repairs. No one took the offer. It ended up going out in the trash.
Later I found that the problem (faulty capacitors) was so common with Samsung TVs that there had been a lawsuit. At that point Samsung started repairing the sets for free. (In one review of the problem it noted that the repair man was working full time doing nothing but replacing capacitors in Samsung TVs.
I wish you luck in getting your set repaired. The cost (if Samsung does not cover it), is about $300.