Hi Phillipe,
FYI: I tried removing mapping from all non-itunes fields with the pretty much the same result:
TIT2: Title = Success
TALB: Album = Fail
TCOM: Composer = Fail
TCON: Genre = Success
TPE1: Lead Performer = Fail
TIT1: Content Description = Fail
TENC: Encode by = Success (though value entered into mapping directly, not from xml)
Damien