iMac - 2" line appeared down the middle of the screen

I have a 20" imac and right down the middle of the screen this 2" line appeared. It is blowing everything out almost like all the pixels are blown...

I haven't dropped it, and when I take a screen grab it doesn't show up. Has anyone seen this? Know how I can fix it? How much it would cost to fix it? I don't have apple care, I know, I'm a fool.

Thanks an advance for your help!

It looks like it may be a GPU problem. One way to check for sure is to hook an external monitor up to your iMac and see if the same 2" line appears on the external. If the same 2" line shows up on the external, the graphics chipset is more than likely at fault. If it is the GPU, the entire logic board will have to be replaced as the graphics chip is integrated on the board. (surface mounted)

Regards.