Miracle!
The answer is to plug the reader to your USB using psp double cable and let it reboot zillion times while it's charging ;>
<the red and orange bliping leds are both on>
This fix worked when nothing else would.
I had to join the forums to say thank you!
I received the PRS-600 as a lovely, very much desired gift this past (2009) Christmas. When to my horror, after my first e-book purchase (I've been enjoying Gutenberg) my reader wouldn't eject. When I unplugged the USB I had the 1fskin:/l/string... error.
For 3 torturous days I tried all kinds of fixes - changing then deleting the media.xml.bak file, having an unsuccessful chat with Sony's online help (who recommended I send my unit in for the exchange program), it wouldn't hard reset, and I did uncountable resets. I just wanted to say thank you so much for telling me how to get my reader back!