I can’t answer your question (maybe Pidgin devs can). Pidgin is a cursed client It is so often that something isn’t working just with that client… Why do you want to use MSN through a gateway if Pidgin (Miranda also) has a native MSN support?
The “to” attribute contains an IP, whereas an component (a jid) should be the case. The IP could mean that you try an service discovery with an link-local xmpp connection. So I suspect you did not choose the right endpoint in the pidgin GUI for the service discovery.
This is more an Pidgin related error. I personally don’t like libpurble. To quote wroot: “Pidgin is a cursed client”. Give Gajim or Psi a try.