I'm having very similar troubles with C5_Pro. Some scenes it flat out won't load. Some I can manage to load after a number of tries, but when I try to render, C5 blinks out. Gone. With still others, I get the "unknown error"s or the "memory allocation error"s. I'm starting to wonder if I didn't have a lot less trouble with "vanilla" C5, rather than C5.1?? Do these problems seem worse on 5.1 to anyone else. We're talking scenes in the 150-225 megabytes range with multiple figures and hi-res textures.

I was also tinkering with the idea of loading scene elements in bite sized chunks. In otherwords, set the scene in Poser, and then save out the scene elements in separate files. Then using Import in C5, rather than Open.

I'm not a happy camper. I switched to Carrara to get away from this sort of problem. Belive it or not, last night I rendered a 'toon in Poser, at medium resolution, that C5 wouldn't even load. Talk about a turn about.