Ubuntu 16.04 LTS cannot shut down

[M. Fioretti]

Greetings,

the title says it all. I installed this version of Ubuntu on an HP 
Pavilion G6
laptop, and the only thing that doesn't work, and makes Ubuntu unusable 
for now,
  is the fact that it does NOT shut down.

- "reboot" from the terminal works

"shutdown -n now" from terminal, or "shut down" from the graphical 
interface
do not work. They only **completely, completely freeze** the system.

I have **already** searched online for this problem, and all I found are 
lots
of reports like this at askubuntu and similar places, with almost zero
answers. Any help to diagnose and fix the problem is very welcome.

Thanks in advance,
Marco


-- 
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