Many applications are designed so you can not use them as root at all, one example being VLC. The reason being that it is not worthy for them to worry about providing security support for when the user makes such decisions.
If the reason you login as root is you don't like typing the password, you should setup sudo to never ask your password instead, and login as a normal user.
Now it work . I don't have error message.
In "sorgenti software" in the third field i removed all repository about opera (I had 2 urls) . Than i reinstalled Opera 40.0.2308.62
Now in repository i have only this URL : deb https://deb.opera.com/opera-stable/ stable non-free #Opera Browser (final releases)
Okay, apologies I jumped the gun based on a coincidence.
Turned out to be a video driver reverting to one that doesn't work correctly (Nvidia Nouveau) that occurred just before, or just after I updated Opera.