I posted this in the model specific thread, but thought I might have more luck in the overall forum...

I got my Mitsubishi WD73-733 in early December. Love the TV, but within the last 2 weeks I noticed that there is a problem. It seems that there is a diagonal "bright spot" about 5" wide extending from near the upper left corner of the screen down to about 1/5th of the way from left to right on the bottom of the screen. This spot is very noticeable in any dark scenes and is clearly visible when the TV is just on a black screen. It's very strange because it doesn't really appear to be an imaging problem, it almost looks like some odd reflection of some sort from inside the case. Has anybody else had this issue? Any ideas?

It could be plastic shavings from the screws that go into the screen frame.

It's a common issue on new sets.
It may also be something inside the set on the mirror or lens, or somewhere else in the light path.

How long have you had the set?
You only have 30days with Mitsu. to report screen problems. After that they assume you have checked out the screen and it's OK, anything else is deemed user damage. Unless it's internal, then you have a leg to stand on. But if it's just in the projection are within the light path, then it's covered by the full 1yr. warranty.