Since it seems to be working for the rest of us, there are a couple of things you could try.
First check to see if SSL connections have become checked by accident. If your client lets you view the raw XML, check to see what error the server is actually returning. Next try a different account, and a different client.
I would be happy to see the Jabber server included in the guaranteed update, but it wouldn’t be practical for the gateways, as Dreamhost (like the rest of the Jabber community) are at the mercy of the likes of AOL and Microsoft for those.
Can anyone give me any hints on the connectivity problems with syndicon.de? I have seen this problem with other domains from DH based Jabber servers before.