asterisk users - Oct 2003 - Zap Analog Line Hangup Problem

Hi..

    I'm having the next problem... with the busy detect = yes...

        If i have it...  The * it hang up the calls when they are 
active... ( Incoming ant Outgoings calls).

        If i haven't it .... * Doesn't detect when some one hang up and 
never close the channels...


   WHAT I CAN DO ????