Inmediate HangUp

I am having a problem with an Asterisk server, in that when it is receiving a call from another Asterisk server using an IAX2 trunk the phone rings for 10 ms and then there is a hungup from asterisk and then the phone rings again before another hangup.

The funny thing is that after I really hang up on the calling phone it repeats this as if I am still trying to call.

Any Ideas?