Emily, WOW, thanks for such a thorough response. I'm sure it will help others, too. Well, the problem didn't pop up again. I think the reason it did before is that I'd been surfing the net, running several apps, all kinds of stuff prior to opening Poser. I did increase my virtual memory settings a bit more, but they were already very high, divided between two drives. After rebooting, I shut down unnecessary processes (e.g. the stuff that iTunes loads at startup,) ran MemTurbo as fis13 had suggested, and was able to complete my renders with no problem. Apparently, this really was a memory issue, although I think it's clearly more a matter of how Poser manages (mismanages?) memory than not necessarily having enough RAM and virtual RAM available.