It looks like the SRV records for dyfis.net are not visible externally:

$ dig +short SRV _xmpp-server._tcp.dyfis.net $

The funny thing here is that the Go Daddy control panel shows the SRV records in question as existing (this domain was purchased via Google to be preconfigured for use with Apps For Your Domain)... so I'm a little bit miffed as to why they aren't externally resolvable.

In any event, though, this looks more like it's on the Apps For Your Domain / GoDaddy side rather than being a configuration issue with Google's jabber servers.