When I try to unregister through Psi's XML console with
<iq type='set' to='aim.im.flosoft.biz'>
<query xmlns='jabber:iq:roster'>
<item jid='aim.im.flosoft.biz' subscription='remove'/>
</query>
</iq>

I get
<iq from="aim.im.flosoft.biz" type="error" to="andy.dirnberger@gmail.com/Psi" >
<query xmlns="jabber:iq:roster">
<item subscription="remove" jid="aim.im.flosoft.biz" />
</query>
<error type="cancel" code="405" >
<not-allowed xmlns="urn:ietf:paramsml:nsmpp-stanzas"/>
</error>
</iq>

Anyone have any idea what's going on?

EDIT: I removed all of the contacts through Gmail and the run-time error that prompted me to change transports became a non-issue.