I'd unplug the unit for a while. Clean the front face of the player and change the batteries (even if new) on the remote. Before you plug it back in, make sure no buttons on the unit or the remote and depressed. Also, make sure there is no other device possibly causing interference.

If that doesn't work I'd call in an exorsist or threaten it with a bottle of 409.

Thank You very much klaa2,

The problem was indeed in the button of the device (TV)
The remote was ok (I had removed the batteries with no change). After pushing the menu buttom on top of the TV it disappeared and everything went to Normal.

It happened 1 time afterwards while watching TV without somebody pushing the button and again it was cured the same way.
I am happy that I can watch TV again and that it was not necessary to call for an Exorcist

Could it be that the connections of the buttom are clogged with dirt since it is located on top of the TV and is collecting quite some dirt.

Thank You so much