There is a 2gb file size limit to all Bryce files, be they image files or preset libraries or whatever. If you are having crashes it is because you are stressing out you rmemory. It doesnot matter how much ram your system actually has, you could have 16gb it makes no difference with Bryce. If you are ever approaching the 2gb limit you will have out of memory and crashes.

I can give you alot of details on the subject, any further questions just ask.