After a user enters his or her account name and password in Outlook Web App, the logon process fails, and the user receives a time-out error message. When this issue occurs, no Outlook Web App users in your Exchange Server organization can log on. This issue may last for several hours until you restart the Client Access server.
This issue occurs because of an infinite wait (or freeze) in the ADNotificationListener method.
To resolve this issue, install the following update:
2961522 Update Rollup 7 for Exchange Server 2010 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.