Assume that you run Microsoft Office Outlook Web Access (OWA) in Exchange Server 2010 Service Pack 1 (SP1) by using Internet Explorer 9. When someone sends you an instant message, you do not receive a new incoming message pop up as expected. Instead, you receive the following error message:
HTTP Error 400 Bad Request
This issue occurs because Internet Explorer 9 changes the way that the caller path is prepended to the URL. However, OWA does not call the functions that respond to the message.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.