Okay, did you change the password by clicking 'PROFILE' on the user-bar thingy? And then went in there and changed it? That could have done it. Make sure that you use the top right box when you change your password. If I remember correctly, press Forgot Password and go from there. It will allow you to change it eventually, if you can't when you are logged in the top box. Either way, try changing it from there.