Problem Description :
Even if you are an Domain or Enterprise Admin you may receive the following error message during logging on to the Self Service Portal in System Center Virtual Machine Manager 2012.
Error Message :
Failed to log on with the provided credentials. Make sure your user name and domain are correct, then type your password again.
1- Be sure that SQL Server Collation is set to Latin 1 General.
2- Create a Self Service User Group and add the Administrator to the Self Service Users.
Good luck !