Many odd things are going on with Google's gTalk server at gmail.com. One odd thing is that I get presence stanzas pushed to me by the server with my own full JID as the from attribute, at regular (?) times.
Another issue is that I am not allowed to send normal messages to myself, at least if I specify my bare JID as the to attribute according to the XMPP standards. However, if I set my full JID as the address, it gets delivered OK.