WOW! I found this thread as a result of a 4805 dust cleaning thread
I know this is an old thread...but older projectors will start needing simple repairs such as this and I wanted to add my thanks to those that have documented this process!
My projector was bought new 6 years ago?...I took to task to cleaning it and when I was finished with the cleaning and tested my work, I found I, too, had the discolored bar running down one side of my screen. I assumed I had assembled incorrectly, so I took it apart and put it back together...no change. I then saw the link in the above thread to THIS thread..and what did I find??? A collapsed tunnel!
I'm sure over the years the glue finally gave in. She's been good to me for all these years, so I figured I'd follow the steps to repair her. Besides, I don't have the money to buy a new one.
Thanks again guys!!!! You have saved a great performing projector AND a man cave in ONE fell swoop!