If Fixing Keychain Access Issues finds an issue that it cannot repair, or if you do not know your keychain password, you may need to reset your keychain. (Resetting a keychain sets aside the original default keychain file and creates a new one.)
Open Keychain Access located in Application/Utilities
From the Keychain Access menu, choose Preferences.
In the General tab, click "Reset My Default Keychain" and authenticate with your account login password.
After authenticating, quit Keychain Access and restart your computer. Your Keychain Access password should now be the same password that you just entered.