I set up a new jabber user, and it shows up as active in the control panel but no clients I've tried can connect (I've disabled SSL in the clients).

If I do "telnet mydomain.org 5222" I get "connection refused" - wouldn't this mean the jabber server is not running on my host?

Correct. It means it isn't running. You might try and connect to the server instead of the domain. (eg. neo.dreamhost.com). That would tell you if the the server actually crashed or the config from the web panel just never took effect.

In both cases you're still going to need to contact support.

digitalrundown.com

I've contacted support, and it turns out jabber cannot be enabled on domains with two consecutive dashes in the name.

This means that internationalized domain names (http://www.faqs.org/rfcs/rfc3490.html) don't work. Bummer :(