umurmur refusing connections after router changed

[karl.i...@gmail.com]

Very strange behaviour: umurmur was working fine on my Debian-based Sheevaplug last week.  Then our router died, this morning I set up the replacement and switched over the Sheevaplug's LAN IP address (it was at 192.168.1.x, new router requires 192.168.0.x), set up port forwarding... and now everything is working again except umurmur, which is dropping incoming connections instantly:

[12:12] Neuverbindung. (new connection)

[12:12] Verbunden. (connected)

[12:12] Serververbindung fehlgeschlagen: Der entfernte Rechner hat die Verbindung geschlossen. (Server connection failed: the remote computer closed the connection.)

(not a native German speaker BTW but I believe those translations are close enough)

The server is definitely up, I can see its ping and connected users (0) through the Mumble client.  I've read through the conf file and init.d entry to verify nothing there needs changed, and restarted the service (and the whole box).  It doesn't make a difference whether I connect over the LAN to 192.168.0.61 or using my Internet domain name.  Nothing appears in the log when I try to connect -- I see the server startup information but nothing about the connection attempt and why it was refused.  I can't imagine why I'm seeing this behaviour, any ideas?