Mine crashes too, but not in the same circumstances. I have scene of medium complexity (don't remember the poly count) and I'm trying to add a little hinge to a port hole. All goes well until I try to save - then it crashes saving nothing. I tried this several times, once loading the port hole into Bryce 5, adding the hinge and saving it. But when I open the scene in 6, replace the port hole, and try to save . . . boom. Now I understand my PC is short on ram and overall horse power and is sometimes a little wonky, but this really shouldn't be that big a deal.

So, I'm rebuilding the scene in Bryce 5 . . . .  with no HDRI (sniff).

Maybe I'll try reloading Bryce 6, but I don't hold much hope for it. Perhaps I can use 6 just to render. hrumph!

"Imagination is more important than knowledge." - Albert Einstein