re: AFCI - Breaker keeps tripping.

Have you hung any pictures or done anything else that penetrated the walls where the circuit runs that could have clipped one of the wires?

What is the brand of AFCI breaker? I know the ones that our builder installed are Eaton AFCIs, and each breaker has a small red light on it that will blink when it trips. The sequence of blinks tells you why it tripped. I would think you would know if yours had this feature though.