Answering a call, ringtone continues on both ends

Hi,

I’m setting up Asterisk in a new environment. Here are 2 uses cases :

  1. IAX2 client on ZoIPer --> remote asterisk server --> regular outside phone
  2. regular outside phone --> asterisk on remote server --> IAX2 client on ZoIPer

Case 1 works fine, both people can talk to each other.
Case 2, when the client on ZoIPer presses the Answer button, the ringtone continues on both ends as if he had not answered.

Can anyone point me to what might be causing this problem?

Thanks

I’m still stumped…

Asterisk 1.6.2.10
Linux version 2.6.18-194.8.1.el5 (mockbuild@builder17.centos.org) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-48))

I can post relevant config files (tell me which) if it can help.