I then can't switch back to the text console (Ctrl+Alt+F1), just a black screen is displayed (I can switch back to X ok). Everything works fine on a non-TwinView system of otherwise identical configuration.
Thanks Archie. The metamode workaround is working for me.
I have gotten a few responses from elsewhere and they are blaming an "acknowledged bug" "conflict b/n the console framebuffer and the Nvidia driver."
I have also read of other problems with X, Nvidia, and the Console frame buffer.
This seems credible to me.. and I am running a console FB.. but now for the newbie question: How do I disable the console framebuffer so I can test this?