"The User Profile Service failed the logon. User profile cannot be loaded.” error message

Microsoft kb947215 said:
Occasionally, Windows might not read your user profile correctly, such as if your antivirus software is scanning your computer while you try to log on. Before you follow the methods here, try restarting your computer and logging on with your user account again to resolve the issue. If you restart your computer and it does not resolve this issue, use the following methods to resolve this issue.
Please see Microsoft Knowledge Base (kb) article kb947215 - http://support.microsoft.com/kb/947215