Error message when you try to send a Subscribe request in Communications Server 2007: "SIP/2.0 481 Subscription Does Not Exist"

When you try to send a Subscribe request in Microsoft Office Communications Server 2007, you receive the following error message:

To resolve this problem, apply the Communications Server 2007 update package for the Unified Communications Managed API v1.0 Redistribution that is dated December 17, 2007. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.