No, it's not a warranty case. It has been known for a long time. It came with the new pdf-reader's crop/zoom functionality. Afaik, the grey dashed lines are supposed to show the "view port" or something similar. I've been waiting for them to disappear since november 2012...
See also here:
https://www.mobileread.com/forums/sho...ed#post2295017
direct link to a screenshot:
http://www.abload.de/image.php?img=2012110700438upk.jpg