Symptoms
A black screen is displayed after you enter your user credentials in the logon dialog box on a computer that is running Windows Vista or Windows Server 2008. When this issue occurs, you can still move the mouse pointer. However, you cannot start applications such as Windows Explorer. After a while, the operating system stops responding.
Resolution
This issue occurs if an event log is corrupted. In this situation, the Event Log service spins in an infinite loop when you log on.