How to block a contact

I am trying to block someone in my jabber contacts.  I was able to block them on my iPhone but am still receiving messages via jabber on my computer.  The block this person option is greyed out in my buddies options.  Can someone explain how to block this contact?
_______________________________________________
This is JUser -- a mailing list for end users
of Jabber/XMPP clients.

To unsubscribe, send email to
[email protected]
or go to the following web
page, scroll all the way down,
and type in your email address:

http://mail.jabber.org/mailman/listinfo/juser
_______________________________________________