I was having so many problems also

But i recently reinstalled zephs rev2 and before i was using mt ati card and i was trying to install the nvidia to an existing install. so when in reinstalled in put the nvidia card in and installed with 10.5.2 Nvidia Kexts and NVinject select and lo and behold it worked with QE/CI i suggest you use pacifist open the install dvd and install those packages. AFTER you remove all other kexts and reboot without any installed. then reboot again and hopefully you will be in good shape. btw im using NVinject 2.0 -256 my card is pcie but you shouldn't have much variation