I installed 14.04 on a machine with an NVIDIA Quadro K600 connected to two LG "Goldstar Company Ltd" 22 inch monitors. One on the DVI port and one on the HDMI port. I was initially happy with the open source Nouveau driver. Everything worked as expected with the monitors using their native resolution. Then I discovered the Nouveau driver wasn't providing hardware acceleration to my VMWare (Windows 7) virtual machine. So I switched to the proprietary tested NVIDIA driver (version 346.96).
At that point I found the second monitor, the one on the DVI port was not configured properly. The information that had previously been detected (I assume via EDID) for this monitor was no longer present. It was available as a generic monitor with a maximum resolution of 800x600 - well below the 1920x1080 it supports. The /var/log/Xorg.0.log also showed many lines of text saying that the EDID information contradicts itself. It's unclear whether that is of relevance. Is it possible the system was trying a poor configuration with the pair a single 3840x1280 monitor?
In any case, I'm sure I need to produce a custom /etc/X11/xorg.conf file, but the NVIDIA tools included with the driver were not useful. Can you help? Please let me know if you'd like to see files etc.