This is an interesting problem. I just spent Christmas Eve rendering a scene that crashed Bryce 6 several times and gave me "out of memory" errors during saving.

Anyway, I am curious. How about, if possible, segment the scene into various parts and render those. Then postwork them back together.

Although my issue isn't the same, it does share some similarities: problem getting it done. I wish you luck, and if you do find a solution, please pass it along!