OK, this exact same crap happened to me on my Sony VPL HS51, it started about 2 months ago. I got the Sony right after they came out, so have had it almost 3 years.
It started in the top left corner going down the left edge just like your image, and then spread across the top after that. It kept getting worse until I sent it in. Thankfully I had a 3 year extended warranty with a 3rd party warranty provider.
Long story short, there's some component they need to replace that will cost them about 1500 bucks from Sony to do.
As a compromise, they are just going to send me a check for 1500, and I get to go shopping for a new toy.
I'm definitely NOT getting another Sony projector. I did not have very many hours, and I've already had to replace lamps twice on this lemon.
While the picture image was clear and beautiful, the upkeep of this thing was ridiculous. Like others, I replaced filters as required.