Problem with my Toshiba 27A44 television. The picture will be fine for maybe 20-30 minutes at a time, then acts up for perhaps 20-30 minutes, then may go back to working fine for a while (there is no set time duration for these events, it varries). While acting up, the picture pinches in from the top and bottom a few inches and every now and then pinches so most of the screen is black. At the same time, the picture will jiggle up and down and then eventually settle down, only to jiggle later. SO, the picture pinches from top and bottom and jiggles up and down for varying durations only to stop doing so at random for varying durations. Do you have any ideas for doing further diagnostics (if needed) or do you have any ideas of what is wrong and how to fix it?