Seems like the Xorg nVidia driver provided with EL5 brings up the primary display just fine, however the secondary display displays only garbage video. Trying to compile a new driver with NVIDIA-Linux-x86_64-1.0-8776-pkg2.run leads to a dead end with prompting for development source which I am unable to locate.
For pre-G80 GPUs, the nv driver supports dual-head only through the "Dualhead" option. It does not support multiple X screens on a single GPU.
*** This bug has been marked as a duplicate of bug 5190 ***