nvidia-settings frame lock issue
I have four projectors and a monitor connected to a PC. When I want to sync the projectors, the monitor stops displaying, even though it is not included in the frame lock group. All projectors are 1920x1200 @ 120Hz, and the monitor has the same resolution, but @ 60Hz. The four projectors and the monitor are configured as separate X screens (so five X screens total).
Some details of the system:
Ubuntu 12.04, using Xfce 4.8 (because the default windows manager displayed a desktop on only one screen, all others being white, including the monitor), nvidia driver 304.64, two Quadro K5000, two stereo-enabled projectors on each, plus a monitor (not stereo capable).
This is a dual boot system, and I do not have this problem in Windows 7.
Any idea what's going on and how to fix it?