Echo Problems !

[svisvanatha]

Hello,  I have an Asterisk 1.2.24 install, which uses my Gizmo SIP
account for outgoing calls.  It is all configured properly, however, I
hear an echo of my own voice throughout the call.  The other party
does not hear this.  Is there some echo cancellation that I an
perform?  Also, I am using the G711 codecs (ulaw and alaw).  Should I
be using another codec?  Thanks for any help or tips.