Okay, here is an update on my progress.

I am now pretty sure I have the latest rtcomm installed. It was harder than it should have been to get there. I had to manually download and install (with dpkg -i) a lot of dependant packages and deal with hiding some symlinks in /etc/rc2.d to make the installer happy. Very messy.

Although I still have the same NAT problem, I then configured another SIP provider (Gizmo) and it worked! So I guess this is an Ekiga problem? Maybe I'll bug them and see if they have an answer.

It's funny, I've had my N810 for about a year-and-a-half and this is the first time I've played around with its VoIP capability. Although it has been fun, I'm not sure yet how practical it is since my N810 is often out of Internet range, and I seem to have plenty of traditional phone services around. In fact I only stated messing around with this to configure my N810 to test a point-to-point Skype setup for a video conference. Too bad the N180 Skype client doesn't do video. I've also joined the masses in waiting for Google-Voice to become available to new users again.