I have the same problem with my GeForce 9300 GS, manufactured by "sentey".
I have a LCD monitor in the VGA plug and a CRT TV in the S-Video plug.
In Ubuntu 10.04 (32 or 64 bits) with the legacy driver 173.14.22 or 173.14.25, nvidia-setting show the two screens, monitor and tv: http://img693.imageshack.us/img693/7544/nvidia1732.png
The two screens works fine but if i try to log out, the system freeze and not responding. Ubuntu 9.10 (32 or 64 bits) don't have this issue with driver 173.14.20, everything works fine, so i downgrade to 9.10 since i buy this card.
I proved a Opensolaris 2009.06 LiveCD that has the driver 180.44 and nvidia-setting showed both screens also.
In Ubuntu 10.04 and 9.10 (32 or 64 bits) with "current" driver (190 to 256), nvidia-settings only detect the monitor on VGA plug: http://img409.imageshack.us/img409/7174/nvidia1952.png
All the attempts in xorg.conf for forcing the tv-out, did not work.