My 52" Samsung did the same thing just at 2 years. You are correct with there being something with the humidity. becasue of an unusual warm summer in San Diego I have run the AC non stop. If I turn the AC off the problem returns to the TV within 2 hours. If I turn the AC back on for 45 min the TV fires off just fine. I have repeated this 6 times now with the same results. Give it a try.. The AC pulls the moisture out of the air and your TV will WORK!!!
Sumsung in hiding from the problem.