I was able to confirm that version 8174 solves this issue.
But versions 8174 and 8178 brought new and previously unseen issues on my Toshiba laptop and GeForce 420 Go. When Xorg starts, the whole system freezes (not even a SSH login is possible). I was able to overcome this problem by passing the following parameters to the nvidia module:
But an annoying side effect appeared: when logging out of X, the console became totally garbled.
With 8178 all got worse. Not even the above parameters prevented a total freeze when X starts... I eventually decided to downgrade to 7676, the last version that behaved in a civilized way on my Toshiba.
What I wanted to know if any of the issues I described affects any other Toshiba users.