Are you making sure your installing the correct version of the drivers. I downloaded the latest nvidia beta drivers (169.04) today - I'm in the UK so I made sure I downloaded the international version as they said the US version will not work outside the US. nvidia.co.uk if your in the UK.
Also make sure you pick the correct operating system. The drivers for my 64bit Vista installed fine. It did freeze when it was restarting, so I pressed the reset button but the drivers still installed ok.
You have probably tried this already but its the only thing I can think of.