I think I may have suggested this before, but you might want to make a very concise post about your trouble on the Defective Mitsubishi DLP thread as I seem to recall someone on that thread having an ear at Mitsubishi.
It seems the particular people you've been dealing with are not good at customers service. Sometimes the wrong people in any organization will give you the runaround, which is what you appear to be getting. This shouldn't be going on for such a long time.
Years ago I had a similar experience with a defective camera, with my patience sorely tested. You definitely need to be dealing with someone else.
Good luck, and try that thread.