I am currently unable to shut down my laptop with Ubuntu 12.04. The screen just freezes during the shutdown process and I have to use the power switch. If I press esc during the shutdown the last messages before freezing are:
/etc/rc0.d/S90halt: 2: /etc/default/halt: INIT_HALT: not found * Will now halt
Sometimes, but now always, it tells me that killing all remaining processes has failed.
None of the answers here have been of help so far.