I've had this with my new one (1.4 Build 9xx), and I found suggestions from 'gerraldo' in May on this thread:
https://www.mobileread.com/forums/showthread.php?t=47468
Here's gerraldo's list (my notations in brackets)
- Only use MOBI/PRC files (you can convert all formats with MobiReader software on your PC).
- Always turn off your reader manually (no [disable] Auto-Off).
- Don't use pre-installed fonts (especially Verdana), but free available ones - lots of recomendations here in the forums. [I copied the Myriad font from my Adobe Reader 8 directory]
- Just use books from the internal memory and don't use more then 20-30 books (bootup will be faster too). [keep the rest on the SD card]
- Always safely remove your reader from USB (either with Windows functions or special tools) [make sure you use the tray safety icon to bring up the USB 'stop' dialogue and stop the Cybook connection]
- Keep your batteries charged well (don't go below 30%, some even say 50).
I am about to delete my unwanted demos -- I'll see if that is a problem.
Richard