Can't open newly-added books on device
I am using an old Gen3 (using firmware 1.0), which was given to me by someone who upgraded to various Kindles without using the Cybook a lot. It had various books already on it, which all work fine. This Christmas I tried to add some new books from Project Gutenberg - ran them through Calibre to make sure the formats matched up correctly, and installed them on the device seemingly with no problems. However, I can't actually open any of them on the device - when I try, it just freezes entirely and the reader has to be reset.
There appears to be absolutely no difference between these files and the old ones which were already on the device, so I am absolutely mystified as to why there is a problem. Would a firmware upgrade help? Or does anyone have any suggestions for things I might have missed?