Does the vertical line show up during the boot screen (restart) ? If so the same happened to me with my SS2 that was less than a month old, it was a hardware fault and I received a replacement from Microsoft.
If it is hardware and your warranty has expired then you are SoL. Best you can do then is to go into your Microsoft live account .. select Devices .. select Support (on your SS2 entry) .. then go through the support wizard. You will have to pay for the serviceing .. maybe you'll get lucky and there is a fix for £300 - £400 . Most likely it will end up being a replacement device than will cost you the best part of £800 (with shipping).