Whoa! Justin Bieber and Usher apparently got into it at Beyoncé and JAY-Z's Oscars afterparty! According to what a close source told TMZ on Thursday, JB and his former mentor were both attending the party on Sunday nght when Usher walked up with "energy and anger." That resulted in a "heated exchange" between the two, which one source claims ended in a fist fight. Wild!!! Related: Justin 'Protecting His Mental Space' Above All Else A separate source in Justin's camp claims there was a tense confrontation - but, importantly, no punches were thrown...