Re: Twinview not working and nvidia-settings crashing on T61 (Nvidia Quadro NVS 140M)
After reading your post I did some more testing.
If I use nvidia-settings to switch to a clone setup using 1400x1050 for the external monitor (which actually has a default resolution of 1680x1050) everything works as expected! After that i can use nvidia-settings a second time and switch to 1680x1050, resulting in a working clone setup (LCD with 1680x1050 and external monitor with 1680x1050)!
Although this isn't a perfect solution it is a good work-around until nvidia will release a better/working driver!
To summarize the issue: Using nvidia-settings with the same resolution (1680x1050) for LCD and external monitor result in only one monitor working and Xserver crashing afterwards. Using 1400x1050 for the external monitor first, and then switching to the correct resolution of 1680x1050 brings up a working setup.
This looks like a driver-bug and needs to be fixed!