I just installed the most recent version of wordpress.
then i changed the passwords one or more times and all of the sudden it said
"Your session has expired" password incorrect every time i tried to login. I even tried to reset my password via e-mail but i got the same problem every time untill i deleted all my cookies in IE then the password i got from the reset thing via email worked straight away.
It seems to me that you have a bug which is that you forget to delete the cookies when you alter the password.
I think i altered my password via bbpress but i have forgotten about that.
Please follow up on this.