My screen has done the same thing. I just went out and bought the 505. I do plan to fight with Sony to see if they will fix the 500 but based on what I've read here I'm not holding my breath since I did not purchase the extended protection plan (which I will be doing for the new one). Has anyone gotten theirs fixed? I did not do anything unusual to cause this (no drops, just carried it around in my brief case).
The good news is that it looks like the old power cord will work with the 505 (no longer comes with one).
EDIT - Looks like I'm SOL without even calling Sony. My 1 year was up on Oct 5th. bummer