Jeni-
All of the traits you are describing could very well be signs of a gifted kid who isn't getting enough (or any?) challenge. It is also quite possible that you have a twice exceptional child who is both gifted and ADD or somehow learning disabled. There may be an auditory processing issue, a visual problem, etc.
I don't like to put too much emphasis on grades, but if a gifted child is getting C's regularly, that sets off warning bells for me. There's something that needs to change.
best wishes-
