When logging into the Symanted Endpoint Protection Management Console (SEPMC) console, keep in mind that the username is case-sensitive.  This is true whether the account you're using is set for 'Symantec Management Server Authentication' or MS 'Directory Authentication'.  You have to match the case of the username as it is listed within the console. The case as set in the console does not have to match case of the username as shown in MS-ADUC when using Directory Authentication.