Similar to the previus post of false ringing.
I have 2 Asterisk 1.6.2 boxes with IAX2 trunk. Box A has a PRI terminated to it. Box B does not have any out side trunks.
When placing a call from box A to a outside destination all is good, however when I place a call from box B to a external destination, the call gets a false ring over the top of the person answering the phone. Calls placed from a phone on box B to a phone on box A are good, its just that last leg that produces it.
can you show what the CLI looks like when this happens? I.E. a call trace?
that is how I have my system setup. PBXBRG is 1.6.2.12 (contains a TE420 with 2 PRI to telco) and PBX1 is Asterisk 1.6.2.6. IAX2 connection between the two.
As voipcitadel said, post some CLI output. Will probably need it from the call on both boxes.
Ok, so i’m a dork. 
I rebooted the machine and now its fine. Sorry for the trouble.
it may be fine, it may not. I would at least look at the logs and verify something else wasn’t happening.
This could easily crop up again.