Unified codebase my ass. If that was the case, I could use my 8800GT under Solaris now.
You can, via *nix driver 169.04. And you will notice in the past that some bugs affected both windows + unix systems and sure enough when a *nix driver was released w/ the fix, the windows driver also had the same fix.
Since you're in the solaris world, just grab the driver here: http://www.nvidia.com/object/solaris...ay_169.04.html
and give it a shot.