It sure it's too late for you, but maybe this could be useful to others: I simply can't leave the PC to work only with Bryce, because is also my work machine, and I'm very short on RAM also. With some larger files (about 100-150Megs), it often freezes, and I discovered that, most times, it's enough to press Ctrl+Alt+Del, select "Bryce (stopped)" and then CANCEL (not End Task) to exit the dialog. I sure as hell don't know why this happens, but doing this, 90 times out of 100 Bryce unfreezes and resume working.

Just my 2c. I really hope you can retrieve your file, 'cuz the image was really beautiful. Let us know.

Stefano