Just my two cents, but check the amount of space left on the drive you are rendering to.

The video driver comment was right on too.  They can get corrupted.  You may want to see if there is a newer one.  If it was rendering before, then the version of the driver is probably not the issue, but it still may be corrupt.

Have you installed anything new?

Have you checked the event log in the admin tools?  Sometimes can help.

You may want to consider resinstalling poser, over your current version. Could be a corrupt firefly file since it happens when you render.  Biggest hassle is adding your libraries if you have a lot runtime folders.

If everything else is working on your system, I doubt it's windows.  Something changed.  Something evil.

Hopefully you don't have any virus or malware running.

Good luck.