i use miranda to connect to jabber -- here's what i set to get it to work:
username: (where the jabber id would be @domain.com)
resource: some string about where i'm connecting from
priority: a number, where the connection with the highest priority should get the messages.
login server: domain.com
i also specify "expert" options of manually specify connection host of domain.com with port 5222.
finally, under advanced i have to check "disable SASL authentication (for old servers)"
hope some of that helps you!