I've made some progress on this bug, enabling Nouveau to be loaded with
acceleration enabled. However, X is **absolutely not** usable: complete garbage
screen, lots of Nouveau errors, only action available is power down the
computer (or reboot). But for using Nouveau with acceleration in console mode,
it works fine.

There are (at least) two main problems:

*   9400M acceleration is broken (resulting in Nouveau locking up on boot);
*   it seems there is a lockup when starting a working X with both cards
enabled.