The smack library and all jabber clients based on this library has the same bug as xmpppy library (python library) and gajim:

http://trac.gajim.org/ticket/3083

Sample message:

<message to='room@conference.server.org' type='groupchat'>\n<x:y/>\n</message>

When smack receive this message, it throws exception and do relogin.

Some people are going to spam in the conferences with this messages.

(Sorry for my english)