I have a Toshiba 42HM66 DLP that we have been pretty happy with. This is a 42" rear-projection unit, for those who don't want to click the link. Several weeks ago, it has developed an annoying problem. The center of the screen has become discolored. It is mostly noticeable when watching very light-colored scenes, like watching an ice hockey game. It has gotten so bad that it mostly ruins hockey games for me. Ordinary TV viewing is not typically a problem, but white scenes are. I originally thought that the lamp was going out. The lamp was having other issues, too. I have replaced the lamp, but the discolored area is still there. Any ideas what could be causing this and how to correct the problem?