Why JET is rejecting the super user password when I can use the same to login to Sun/User Manager?

The password length for JET is 10 characters. If your Sun super user has a password length longer than 10 characters, it will be truncated after 10th character when using to login to JET therefore rendering it as invalid password for JET. Make sure the super user password length is less than 10 characters so that it is accepted by JET.