I analysed a problem I had with the kraken IM gateway, but it came out that this was not a solely problem of the IM plugin.
I noticed that Trillian does send a 0-byte at the end of some messages. This 0-byte results in a XMPP message like this beeing created:
Such a XMPP message, containing the encoded hex 0 (�) in the body, makes many XMPP clients do a reconnect. I can use Gajim to send such a message I created manually to Pidgin, Adium, Gajim, and it makes them go offline. I checked this with Openfire, I can see the message arriving at the receiving client just like I sent it, and the client goes offline. I also sent such a message to a friend who uses jabber.ccc.de, and the message got dropped by the server before reaching the client. I think it would be a good idea to filter such invalid messages on Openfire too, but I would prefer that the message does not get dropped, the invalid characters should be removed.