mirroring displays and vblank syncing

I have a need to mirror the content on two identical displays, so I have set them up in Twinview to be overlapping. I am showing a moving on the screens, and the problem is that one of the displays looks great while the other has tearing. These monitors are both connected by DisplayPort to a K2000 card.
This link http://us.download.nvidia.com/XFree86/Linux-x86/1.0-9755/README/appendix-e.html states: “When using __GL_SYNC_TO_VBLANK with TwinView, OpenGL can only sync to one of the display devices; this may cause tearing corruption on the display device to which OpenGL is not syncing.”
Any thoughts or suggestions?

If the two displays are really identical, and they’re using identical mode timings, then they should be locked together automatically. Can you please run “sudo nvidia-xconfig --mode-debug”, restart the X server, run nvidia-bug-report.sh, and attach the nvidia-bug-report.log.gz file? That should help determine whether the two monitors are actually running with the same timings.