You may be on to something. I decided to test your theory...I have the King James Version of the Bible on my 505 (the one downloaded from this site not the one from the Sony book store). When I changed the font size to medium it did it just fine--that was at 5715 pages. I then tried to set it to Large size and my reader appears to have totally frozen. So, if this is the case, it looks like the maximum number of pages is something greater than 6368 (based on winspiration's experience).
I've had not problems with the bible at all prior to this--reading from it quite frequently in small size font.