TiBook Display Problem

I'm guessing this is bad. It happens every time I go to screen saver (RSS viewer) and I have put it to sleep for a few minutes before it goes back normal.

I have a 15" TiBook 1 GHz, final series before AlBooks

Please help - I can't afford a new computer and AppleCare's run out.

 

I did that a while back, but the problem returned within a couple of days. Thanks, though.