IAX2 - Registration Refused Cause Code :29

Good Evening,

I have two systems with TixBox on both..

A - Connected to Asterisk 1.4.16-1
B - Connected to Asterisk 1.4.20-1

Attempting to link the two with IAX2 trunks.. A --> B Status is OK (16 ms)
B --> A Status is UNREACHABLE

Both are setup as type=friend only the A box shows that inbound connection and refuses it with a code 29.

Rx-Frame Retry[ No] -- OSeqno: 000 ISeqno: 001 Type: IAX     Subclass: ACK
   Timestamp: 00008ms  SCall: 00649  DCall: 00001 [w.x.y.z:4569]
Rx-Frame Retry[ No] -- OSeqno: 000 ISeqno: 001 Type: IAX     Subclass: REGREJ
   Timestamp: 00017ms  SCall: 00649  DCall: 00001 [w.x.y.z:4569]
   CAUSE           : Registration Refused
   CAUSE CODE      : 29
 

I have looked at the entries and both side look right !!! Anyone have a better feeling for what the Cause Code: 29 is pointing me to ??

TIA...