When I turn my TV on there is a black box on the top left corner of the screen. It is completely black and it doesn't move or change whether I watch TV, change the volume, or watch dvds? Help! What has happened and what do I do?

I had a similar problem on my Panny too. There are "driver boards" that control segments of the big screen. Depending on the size (you've got a BIG one!) there will be several of these around the perimeter of the plasma panel, and they can be replaced individually. You might even get lucky and it is just a connection problem (which would make the box black).

Here is a photo of the problem I had. As you can see, it just affected one color in my case.

Good luck,
WallyH