The last couple of crashes happened on startup (I always switch off the device after using it).
I also use txt a lot. Many books are bought on Mobipocket or Fictionwise...
The others are (always) built on Mobipocket Creator...
So I really don't understand the crashes either... But, and as I said, once a week is not serious or too disturbing since I use my Cybook nearly everyday.
(completely off topic: does anyone knows when will be available Mobipocket Creator for Windows Vista? Windows 7 is already on the door, for God sake!!!) Did Mobipocket give up on this software? Or as Amazon ordered them NOT to upgrade it?!