A post on the MobileRead forums hinted at my Cybook Gen3 stability issues being related to the font face used for displaying text, so I’ve replaced the very lovely Liberation Serif with the slightly less lovely, but nonetheless enjoyable DejaVu Condensed Serif.
Lo and behold, the stability improved tremendously — my Cybook hasn’t crashed once since I’ve switched.
So, yes, the crashes/lockups are definitely font issues. The more you know.