I'm sorry to hear that you're having this issue.
Unfortunately, with no way to determine the cause, I don't have much in the way of advice on how to fix it. I'd recommend having the unit inspected by a technician.
Switched TV off at mains whilst on holiday and everything OK. On return when it powered up there is a thin black line (top to bottom)about 2/3rd of the way across the screen. I've tried switching off. I've checked all the external cables to ensure they are not loose. TV purchased May 2009.
Can anyone help? Thanks