Unfortunately, all TV models have a failure rate, usually in the low single digit percentiles. If your TV worked for 3 years and then started to break, that is outside almost all manufacturer/store warranties if you didn't also purchase an extended warranty. Some TV manufacturers have higher failure rates than others, so at least you can minimize your risk of your expensive new HDTV being a lemon.
I know it is in the past, but LG plasmas (especially 3-5 years ago) have huge reliability/failure issues, which are documented online in forums (like you said). I'm guessing you will be stuck with buying a new TV since LG and Sears will not help you out. When you buy a new one, go for a company with better reliability rates and also check out Costco since they double the manufacturer's warranty for no extra fee.
I'd shoot for Sony, Samsung for LCD (maybe Vizio if you get it at Costco), or Panasonic for plasma.
I would like to see a recall on this T.V. that I bought at Sears and after less than 3 years of use is on the blink. Muted picture with sound. Sears told me(even though I bought all my appliances from them and have been a good customer for 45 years)that they only cover ONE month guarantees (Whatever happened to
CUSTOMER SATISFACTION GUARANTEED??) No different answer when I phoned LG customer service--SO Sorry. What makes me so angry is that they said they have not receved any other complaints about this product!!! I said I found that hard to believe as I had seen some forum complaints on computer. Is there any way I can get some satisfaction or do I just need to suck this up and expect to replace appliances every 2 to 3 years?? They sure don't make things like they used to!! An Irate Consumer