I have a dual-screen set up and on one of my screens, thin coloured vertical lines have started appearing (and staying).
I'm inclined to think that if it was the graphics card then the lines would appear on both screens. Am I right? I do hope so.
I know I could swap them to check, but I'll take any opportunity to avoid faff.
My Uncle's TV has done this but is the t-con I think. Sounds daft but before you over faff, have you checked all the connections to it are good? Shouldn't be the card if one is good.