Hello and thank you for giving me your ideas,
like you suggested, i tried to add differential pair parameters set everywhere, didn't solve the problem. In fact i have even more error now (same type).
interesting fact, compiling on altium 16 doesn't output these errors.
this look like a failure to link beetween sheet and/or wire, but why that's a mystery.
my current license don't include PCB so i can't answer to your first question yet. as soon as possible i'll try with my teammate who have it (altium 15)
EDIT: on A15, the PCB doesn't import diff pairs, and thus while looking at the classes, no diff pairs appears (my apologies if i'm unclear on this part, i'm not used at all to the PCB interface/concept) that will for sure bring some trouble to the project