As far as removing PolicyKit, I have not removed it. I am not in a position to make such modifications.
What do you mean with you are not in position to do that? Running as
root you are in position for everything

Anyways i ask you to double check in
Settings -> Settings Manager -> Session and Startup -> Application Autostart if
PoliciyKit Authentication Agent is enabled. The fact that you are unable to mount, shut down, reboot etc. usually happens with
PolicyKit disabled, so first thing to check is that.
Also try to mount from command line and post the output you get.
Then please, don't run as r00t, really pleease

Then i guess you searched the web... there are lots of threads on various forums, most users experienced this in
XFCE. It coul be something related to
Thunar file manager and/or login manager (default is
lightdm in BB). But these seem old issues.
If you cannot solve, wait if other users have the same issue here, because if everyone running BBox has the same problem we can report to developers.
Otherwise if you are the only experiencing this, it could be a problem of yours.
Personally i have no problems to shut down and reboot in virtualbox, and i'm currently up to date with packages.
Waiting for updates...
Good luck and have fun!
