Underneath the place for links and email notification it says "Post with different username" and a show/hide link button, click that and change the username there, that may work if logging out doesn't, also, you probably should change your default background color to a different shade (Your Account ----> Edit Profile ---> Colour Scheme) as that can help avoid a repeat, we had a lot of these sort of issues way back when we were useing throw away names for one game.