Don't have much to add to the comments, except that i agree with most that has been stated, and urge everybody to watch this film.

About the Norway sequence. I found it wonderful, and it is one of my favorite scenes in the movie. I think that the girl was real, but that both didn't know where she lived and that Paolo didn't have any real contact to her. As was often the case with him, he didn't care much for the dividing line between fiction and reality, as we can see in his daydreams that take on a concrete shape and existence for him. The journey was purposefully made on a Sunday, and they just went to some shool there. Th point of it was imo, that Paolo tries something to come closer to his dreams/hopes without being rejected (Imagine a scene were he actually meets the teenage girl... probably wouldn't have helped his self-esteem). This journey and the rest of the scene can be seen as the breakthrough in the relationship of father and son, because the father enters and accepts the world of Paolo, while still trying to alter it. This journey will probably stay in Paolo's mind as a visit to his girlfriend, and meeting her isn't the point here (Paolo also doesn't want to meet her, and has no problems leaving again). They leave symbolically the cake for her.
For me this is the closest sequence to the "magical realism" (or even surrealism) you can find for example in Fellini. Contrasted with the confession-scene by Rampling at the train station this makes for a wide range of expression. 
"Stolen Children" (1992) is full of such "absurd" events, and one of the main reasons why I loved it.

I know that I wrote earlier somewhere on the board that I'm glad Le conseguenze dell'amore (2004) won the David di Donatello in 2005, but after watching this film I have to change my opinion.