At least Chameleon RC3 has an problem with the boot.plist. Its not used when on USB.
Have you also installed it on Hd and can boot from there (not from USB stick) ?

First i would give an -v (verbose) as kernel flag (after F8, TAB) / getting the Chameleon boot screen.
So you can see how far it boots up.
If you see nothing special, it can be an problem of :
efi string is not OK:
- wrong PCI slot (pci slot is within the efi string), should only happen if you NOT made that own with efistudio and used 1:1 from an other user (which has gpu on different PCI slot)
- NVCAP (info where the gpu puts the screenoutput: DVI1, DVI2, VGA, HDMI - if wrong (NVCAP from other card, other user)) no screenoutput.
You can try change DVI port and / or check your NVCAP efistring (efistudio!)
There is an NVCAP Tool (OS X) , which can show you the needed NVCAP values in hex.
It needs only the .rom file of the card (DL from vendor, extract with gpu-z, ntibitor under Win)