Update.
The lines came back yesterday.
I disconnected the monitor plug at the computer, can't disconnect it from the monitor.
The problem is definately in the monitor plug or computer socket. When I plugged the cable back into the computer, no lines.
Like fatlander said, it could just need a cleaning.
I have to put that on the list.
But it's time for something to take a crap, I think the warranty has run out.