OK. I finally got TwinView to work on my shuttleX .....
But I don't know how I did it..
My XFConfig file got hosed somehow, so X wouldn't start. I eventually ended up with a fresh XFConfig.
I downloaded the latest kernel from RedHat today, re-installed the latest nvidia drivers, and presto! change-o! It worked.
That's all I did. Honest.
Attached is the working XFConfig file I used.
You might need to change the keyboard back to the 105 type.