I will try to help you with this question.
I am afraid I have bad news for you,but being a professional I have to give you the correct information,even though it may not be what you expected.
The issue with this tv set is the LCD panel.
There is nothing you can do to fix this issue.The tv will need to be serviced and the LCD panel replaced.
Now,this is a 2007 model unit,unlikely you still have manufacturer warranty left on it.
Unless you have purchased an extended warranty,that will cover the repair on it,it will not be economical to repair it.
The LCD panel will cost somewhere around-$800-$900.Add another -$150 as labor fee,and the total repair will be around-$1000!
You can buy a 50" plasma tv for this money ,I do not believe you would want to get this repaired at this price!
Like I said,I apologize for the bad news,I know it is frustrating that such a fairly new tv developed such an expensive to fix issue,but this new technologies are all cool and fancy until the sets break,usually soon after the manufacturer warranty expired.
My advice,ALWAYS buy an extended warranty on expensive tvs,since,LCDs or plasmas,they will break sooner or later,but at least you have piece of mind for several years.
I hope this clarifies this issue for you,
Thank you and Happy Holidays!