I have a Sony KF42WE620 LCD Projection TV and noticed that the picture looked like it had smudges or blotches on it. The blotches looked worse on red images.
After reading a few different forums, I decided to venture into the TV and see if I could clean it myself. It is definitely an adventure.
I created a web page with detailed instructions on removing the complete lense, prism and LCD matrix unit for a thorough cleaning at the following web page: http://repairs.sunnyoasis.com/sonylcdtv/
Even though I added a disclaimer to the web page, feel free to post followups and I will try my best to answer any questions.