From what the user can tell, no specific environment or part file triggers it.
He has already set graphics to Direct3D.
It does not give a submit report dialog after the error, it just completely shuts it straight down, no questions asked.
The machine has 2GB of RAM.
However, I just discovered that the video is NOT nVidia as I originally believed (the rest of our workstations ARE nV workstation-class cards). It is running an ATI Radeon 9800 Pro, which I'm guessing isn't a certified card for Inventor... I will check/update video drivers tonight and see if it continues to misbehave tomorrow.