The video card driver is the most recent available, just re-installed today to make sure.

Windows 7 is completely up to date with the latest downloads from Microsoft.

All my other high-end graphics software (Poser 2010 pro, ZBrush 3.5, Hexagon 2.5) is working perfectly fine.

Nothing has been installed after Carrara ... because I have re-installed Carrara completely several times today.

Carrara did work previously on this machine with this hardware and system configuration.
It stopped working suddenly, and the only change was the latest system updates from Microsoft.  But I can't see anything in those updates that would have caused an issue.

I have tried changing some settings on the NVIDIA video card's options, but no combination seems to have any effect -- and why did it work before but not now?  It doesn't make sense.