Voipbuster - no incoming sound - why ?

Hi NG

I have tried to setup Voipbuster on an HT286, RT31P2, X-lite .. and
always with the same result: the other party can hear me, but i can't
hear the other end.
At the same time I see that many succeeded in getting normal 2-way com
going. What the heck can I be doing wrong ? I tried with
sip.voipbuster.com and stun.voipbuster.com (as suggested elsewhere) ..
tried port-forwarding ...and at the end of the day only the Voipbuster
softphone works.

Suggestions welcome. Btw : I'm a Taurus, if that has anything to do
with it :-)