Whenever i turn off the mains, i get a Demontration message after power on.

From the manual:

Demonstration Mode
The demonstration will activate the first time you turn on
the power. When the demonstration starts, the following
message appears in the display:
“NOW DEMONSTRATION MODE IF YOU FINISH
DEMONSTRATION PLEASE PRESS POWER KEY
WHILE THIS MESSAGE APPEARS IN THE
DISPLAY THANK YOU”
To cancel the demonstration
Press ?/1 to turn the receiver off while the above message
is being displayed. The next time you turn the receiver on,
the demonstration will not appear.
To view the demonstration
Hold down SET UP and press ?/1 to turn on the power.
Notes
• Running the demonstration will clear the receiver’s
memory. For details on what will be cleared, see
“Clearing the receiver's memory” on page 15.
• There will be no sound when the demonstration mode is
activated.

and...

Note: If the AC power cord is disconnected for about two weeks, the receiver’s entire memory will be cleared and the demonstration will start.