I installed the openser.cfg at <a onclick="return top.js.OpenExtLink(window,event,this)" href="http://voip-info.org/wiki/view/OpenSER+And+Mediaproxy" target="_blank">http://voip-info.org/wiki/view/OpenSER+And+Mediaproxy</a>
(modified to authenticate against my domain, and to use exit instead of break). Calls between two phones on the domain work, but there is a lot of jitter. Well, not exacty jitter, but kind of a pulsing sound in the background of the call. Also, will occasionally drop out, and then come back after a little bit.