I am having the same problem, except I am trying to dial into a conference call and it won't except my PIN code. It seems that the DTMFs (duel-tone multi-frequency) for touch tone dialing are sticky or don't go through well. Once, the system repeated back to me the code it received. It heard a repeated digit, and missed a digit. IE i was trying to dial 492 and it got 449. It did work with a 2 digit access code, but only after i made 2 or 3 attempts.
How do we fix this!