Not Authorized

Here's my situation. I have users authenticating using a custom PHP script. I then have a PHP client program (using class_Jabber) logging in every so often, checking for messages, possibly responding to them, then logging out. I'm having a a problem with this setup. A user will in their own client (Pidgin for example) send a message to the user the PHP client logs in as. The Pidgin user may just leave the chat window with the PHP user open all the time, and the PHP user's status will change from online/Available to offline. Occasionally though, that user will change to "Not Authorized" and it seems like when that happens no offline messages get sent.

One solution I like would be to just disable the whole process of users requesting auth from each other. How can I do that?