A General Comment
I do not post to these sites very often, but in this case it might help a person or two. I have an Ultra 2x machine and have been trying for some time to get the nvidia drivers to behave correctly for a dual monitor setup. The one thing that cured the most ills in this case was to make sure that the nvidia driver was recognized on the correct PCI slot on the machine. The solution came from using "scanpci" and seeing the error related to no device found. Once I put this together with the update_drv hint on the FAQs in the full installation guide that I downloaded (not the one that came with the Sun computer) it all worked and the rest was easy. For beginnners and people who manage these systems part time or because there is no other choice like myself, this might be at the top of any list of hints on getting the drivers to behave correctly. A user can reinstall the drivers as many times as they want. However, without that update nothing happens.
Hope this helps someone out there.