Re: GeForce GT 240 and Viewsonic
You shouldn't need any driver for the monitor.
Your logs show that the NVIDIA driver isn't getting initialized. Was the new monitor the only thing that changed?
You also have the ConnectedMonitor option set. Did you do this to try to force the monitor to be enabled? What happens if you start with a fresh xorg.conf? (Rename /etc/X11/xorg.conf to something else, then run nvidia-xconfig as root to generate a new one.)