[frostschutz]

Don't see an attachment, but taking any PDF file and giving it that name (including the folders), causes the loop for me.

It's not a hardware issue. You can send the device back but it won't help you, best case you'll be without your reader for a couple weeks, worst case they claim the display is broken or whatever ... better not risk it, esp. considering the workaround is so easy (just pick a shorter name)

EDIT:
This time around the loop came back even after deleting the offending path on the SD card. Had to delete system/bookDB* on the internal memory to get rid of it