Your old connection prolly hadn't timed out yet.

Prior to 4.2, if you suffered a 90k, you would have been unable to log in due to a 3102 error (character already logged in). You would have had to wait until your old connection timed out and the server closed out your character data. As of 4.2, however, trying to reconnect tells the server to boot the old you so that you can get back on.

This is a great thing! (Trust me, I was 3102ed for over two whole days once.)

You use a security token, so I wouldn't worry too much.