I am very afraid I have no good news for you.
What you have is a LCD panel that has failed, this is a very common problem with these new LCD televisions and there is no way to fix it. The part price is always more than a new television. For example the part needed to fix your set is over $700, you can buy a new set for that price. Unfortunately there are a lot of good folks in your position, they have bought these nice sets, and after 18 months the tv is going into the garbage unless they bought an extended warranty on it.
The only bit of advice I can give you if you don't have a warranty is to call Sony and complain to them, a lot of manufactures are working with their customers because these sets are failing so prematurely. A lot of times the manufacture will repair the set, or supply the part at no cost, leaving you with the labor for installation.
I am sorry I have no good news for you, please let me know if there is anything else I can do for you.
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