on a dark background scene, i can see what looks like a few faint lighter spots in the upper left quadrant of my screen. are those caused by the screen...or projector? they look sorta like when the sun shines directly inyo a lens and you get those bright spots.
This is probably something you'll have to figure out yourself -- its not something that has come up before (as far as I know).
Some things to check for. See if its something behind your screen that is reflecting back some light passing through. It may be the reflection of the brighter part of the scene from the wall behind the screen.
It could be something reflective between your projector and the screen. Say a glass top coffee table is getting some light spillage and hitting the screen.
It might be the projector as you point out.
Try putting something in front of the screen (a sheet of paper) and see if the light is coming from the front or the back of the screen. Then try to trace it back to the source..