[Users] mediaproxy problem

[unplug]

I am using openser with mediaproxy enabled.  All device behind NAT can
make/receive call without problem.  However, when an end device
connect to the openser directly using public IP (without NAT), the
following problem will occur.

-when make outgoing calls, I can hear the receiver but receiver can't hear me
-when incoming call, it works as normal

Does modiaproxy can handle device using NAT and without NAT?  How can
I solve the above problem?  Is it the port setting problem?

Below is the dial plan and the ini file of mediaproxy.
http://meerkat.no-ip.com/openser/openser.txt
http://meerkat.no-ip.com/openser/mediaproxy.txt

Thanks, unplug