If your computer remembers your password, it sometimes can be necessary to delete these credentials manually (e.g. after you have changed your password)
- Open 'Run ...' from the Start menu.
- Type in the following command 'rundll32.exe keymgr.dll, KRShowKeyMgr'.
- Find the credentials you want to delete in the list and delete them.
(Just do it. The only thing what will happen is that you have to type your username and password in again, next time you want to gain access.)