After yesterday's update, a number of people seem to be having problems logging in. If you try to login and receive a message that your password is invalid, please try clearing your browser cache and logging in again. Google search will tell you how to do this. Quick links for common browsers: Chrome Firefox Internet Explorer
I just encountered this problem with an error message something like "Incorrect password for {0}." I fixed it using the link for chrome above, but I had to first come to the forums and find the post. I think a lot of users might get frustrated before finding the solution. Maybe when the error is displayed, a suggestion to clear your browser's cache could be added?
I managed to sort this problem when it happened to me, by submitting a password reset request and changing the password to exactly the same thing as it was before.