Lessee...I've got a Compaq Athalon laptop with 512 MB of RAM, 11.6 GB out of 32GB available on the hard drive, I'm running P5 and working all my files from a USB HD that has over 50 GB of free space, and I've had the last two images I've worked on refuse to render at all when I use default lighting, nothing special. Neither of these PZ3's go over 51 MB in size. I even installed a RAM cleaner and that seems to have made the situation worse. I'll dig around and see what else I may need to do after following the above advice. Thanks everyone!