I created a rule to block chatenabled.mail.google.com and talk.google.com...worked great.
For testing, I created an alternate rule to block the entire IM category...worked great as well. (Thanks for your help, Community!!)
However, the jabber google talk client is not being blocked. I know there is a way to proxy/block XMPP traffic for these clients. I found the setting under Configuration --> Proxies --> XMPP. For the listener IP, 0.0.0.0 is listed. Do I just change the IP to the MWG appliance and will that automatically inspect/block the traffic or is there more to it? I'm guessing this will block all jabber clients...can you just specify the Google Talk one? Thanks for your help!