power management not working

[Thomas]

Good evening
Again me, but with a different question/problem.
The power management of the 14.04, 64-bit installation DID work after 
the installation (as far as I can recollect).
Today I started the computer -
* there is no battery icon in the bottom panel
* an error message pops up at startup, saying something like: "No valid 
power management backend ..."
where I ASSUME, the message goes on, but it does not show on the screen 
and clicking on it does not display it.
Under "System settings -> Startup and Shutdown" it says the power 
management is running.
Yet, it definitely does not work.

Any trick to make it work?

Thank you
Thomas