OK, this is what happened and what I did.
When starting the car with a very low batter the Navigation data disk in the unit jammed. The unit thought there was no disk and asked to load one. Since the disk was kind of jammed, when opening the face of the unit the disk could not be ejected.
I did remove the unit, remove the mounting brackets, the top cover and then the front face (black plastic). I did re-apply power with the front face kind of hanging down and this time the disk ejected (you have to press the LCD display at the top right corner to eject the disk)..
I then found out that I had to re-load the unit with some basic software (in disk n. 1), like when the first time the dealer did. Then it worked fine, after I put everything back together:lol: