I was trying to visit a site protected with HTTP auth, and the auth dialog was prefilled, because I had previously remembered the credentials. But the login was always failing, it seems the password changed. But introducing the new password doesn't work, when you click on authenticate again the login fails and the auth dialog is prefilled again with the old password. I guess we are assuming that an stored password always work, and when found in the keyring we don't use the entered password at all. The only way to log in was to change the password in the keyring manually.
According to Carlos this was probably fixed with the move to the network session. I tried to reproduce it and couldn't so he's probably right.