A long time I haven't been on Mobileread, but today I decided to look for advice on a case... Just like this one !!
I was shocked to discover this morning that my PRS-500, which I hadn't used for a week, displays just the same kind of pattern on the left part of the screen !
Looking at the screen closely, I can't see any crack on the glass itself, everything seems to be inside the device. The last time I dropped the device (and only one I can remember of) was 6 months ago, a few weeks after I got it, and it didn't stop working for that (just got a scratch on the silvery edge).
I am going to try to see what Sony says about this, and if this could be repaired under warranty. Who knows ? Maybe they have a problem of reliability with some components. I hope that me being in Europe is not going to make a problem !