If you cannot log on to a computer that is running Windows Vista, Windows Server 2008, Windows 7 or Windows Server 2008 R2, then this article may interest you.
When this happens, you will usually get the following error message (Event 1502):
Unable to log you on because your profile could not be loaded, please contact your administrator.
This issue may occur if Windows cannot load the locally stored profile. Possible causes of this error include insufficient security rights or a corrupt local profile.
To resolve this issue, you can request for and apply this Hotfix from Microsoft specified in KB2065362.
How to fix Error Message, The User Profile Service failed the logon. User profile cannot be loaded may also interest you.