Please describe the problem:
After a fixed time online making and receiving calls or idleing, Ekiga can't receive calls until it is restarted. It can still make calls normally though.

After the problem has occured, ekiga won't quit properly using the quit menu and the systray icon is frozen until the process is killed.

Steps to reproduce:
1. Launch ekiga with previously configured sip accounts. Ekiga registers them on startup
2. Make and receive calls or do nothing during 50 minutes
3. Make a sip call from another account using another internet connexion to any of the sip accounts registered in ekiga. You don't receive that call in ekiga.
4. Quit ekiga using the Quit menu (Ctrl+Q) : the systray icon stays frozen


Actual results:
From a network dump of the session I observed the following behaviour :
- Every 10 seconds, Ekiga sends a few CRLF UDP frames to every SIP registrar. At the bebinning of the session it sends 3 frames to ekiga.net and 2 frames to the other registrar ; after 49 minutes of idleness, just before the bug, it sends more than 200 frames every 10 seconds to ekiga.net ! (and still only 2 frames to the other registrar).
- There are several SUBSCRIBE and NOTIFY exchanges with ekiga.net. After "The bug", the server keeps sending NOTIFY requests but gets no answer from Ekiga.
- The other registrar sends a "OPTIONS" request every 60 seconds, that is answered by ekiga. After "the bug", the server sends a request per second but gets no answer from Ekiga.

Expected results:
Receive calls until ekiga is closed, without time limit.
No freeze on shutdown.

Does this happen every time?
It happens every time on every version combination and internet connexion I tried :
ekiga 2.0.12 (ubuntu intrepid ibex), (Mandriva 2009.0)
ekiga 3.0.0 packages (Mandriva 2009.0 backport)
ekiga 3.0.1 packages (ubuntu intrepid ibex backport)
ekiga 3.2.0 packages (ubuntu janty fresh RC1) and 3.2.0 sources (ubuntu intrepid ibex)

using ekiga.net, freephonie and a business sip accounts, one after the other or at the same time.

tested both from home (ADSL, nat with isp router) and work (fiber, nat with professionnal router).

tried activating and deactivating stun, using the proxy of the business provider, changing the ip_conntrack_udp_timeout kernel setting, and changing the delay setting in the Edit Account. 

Other information:
I tried with Last releases tarballs (PTLIB 2.6.1, OPAL 3.6.1, Ekiga 3.2.0) from ftp.gnome.org. I couldn't manage to compile ekiga (opal and ptlib compiled ok) from latest svn/git as of 23/04/09.

The time between ekiga startup and the problem occurs is almost the value in the "delay" setting for the sip accounts. 50 minutes (~2980s) is the maximum value after which the delay setting has no effect : it stops after 50 minutes.

Twinke and x-lite on windows works out of the box with the same accounts and internet connexion.