Hi. I have started rendering a few scenes with lightwave 7. This has entailed my computer being on for days at a time. After a render when I try to shut down, my macs desktop clears, the desktop picture stays, and the little spinning clock thingy keeps spinning and spinning. I've left it as long as 2 hours and I always end up having to do a hard shutdown. No key combination shutdowns work. I have to hold the power button. I have made sure nothing is running, relaunched the finder, even tried logging out then shutting down. It only does it after rendering for a long time. I am using 733 quicksilver 640 ram 40G system drive 60G media drive. Any ideas?