I do not think there is any real issue here... James loves to cut up during her concerts, and she was just making the audience laugh... She appeared with Beyonce at the cadillac preimiere all friendly and gracious, and she immediately admitted that what was said was nothing serious...
Secondly, I am not a Beyonce fan, but her role in Cadillac, esp compared to her previous acting endeavors, was fairly good...
ANYWHO, someone on youtube did this well edited duet of James vs Beyonce singing the song... I think we are just use to the song having a much richer voice than B's
http://www.youtube.com/watch?v=qRCV7JGJOsk