Why are vertical and horizontal lines on my TV?

When I turn on my TV there are lines on it like on the picture below. After some time (half hour) the TV is functioning well. It -nééra time to heat up.

What could be the problem? If T con board was faulty it shouldn't get better after some time.

[IMG]http://i68.tinypic.com/2i6gvtv.jpg[/IMG]