KB Article: http://support.microsoft.com/kb/2589415

INTRODUCTION

 Consider the following scenario:

• You configure Microsoft Outlook 2010 to publish and retrieve Internet free/busy information that is stored on a server.
• The server uses the HTTPS protocol and requires a password for authentication.
• You publish Internet free/busy information to the server by using Microsoft Outlook 2010 on a computer that is running Windows 7.

In this scenario, you are not prompted for authentication. Additionally, the Internet free\busy information is not published or retrieved successfully.