I made this trial with a freshly installed Ubuntu 12.10.

Actually I tried the procedure 4 times (all fresh installations, 3 with 12.04 and 1 with 12.10) but the result is always the same. At least for the 12.04 I have the problem of the dependencies on nvidia-current.
In any case ok, as the system now is using the nvidia only and it is very hot and power consuming, I will try a further time. It would have been more efficient to understand where the problem is before retrying following the same procedure without modification but unfortunately I really cannot figure out