That's 99% bad LCD. SPecifically - detached LCD panel from board at the top of the TV.
Happens due to heat and, of course, suckish quality.
Some people fix it by applying physical pressure there and sometimes that even works.
I've done it and I can report first hand.
I can also advise against it because you get to get to the very bottom of the LCD assembly and while this is not a rocket science (it's not exactly trivial either), the stats are that 8 out of 10 times you;ll end up doing more damage than helping.
I have a few TVs with similar issues in the shop and I just treat them as junk. I pay for them as junk, I don't rush to fix them since I know from experience that most of them won't ever be fixed.
Please don't kill the messenger :-)
Use your TV for as long as you can as it is.
When you decide you;re done with it and don't care if you;ll break it carefully insert a credit card between the LCD panel and the front bezel. It should go at least 2-3 millimeters in; there might be a metal frame there - make sure you insert the card between the LCD itself and whatever is pressing it. Go as deep as you can.
Then start moving the card - that;s going to be tough - so that you apply pressure along the length of the display. It should be at the upper side where the vertical line begins.
See if it fixes it, but don;t hold your hopes too high.
At
http://blog.coppelltvrepair.com we have some articles for hacking TVs, but I don;t think we have one for this yet...I might post something if I have time over the weekend...as I said I have a few TVs waiting just for this...