Microsoft Office Communications Server 2007 R2 Hotfix KB 968802
This hotfix download for Microsoft Office Communications Server 2007 R2 is described in the Knowledge Base article 968802.

• Update for Standard/Enterprise edition Server Back End
  982614  Description of the cumulative update package for Office Communications Server 2007 R2 database: May, 2010 Update for Unified Communications
• Managed API 2.0 Core Redist 64-bit
  983568 Description of the cumulative update for Office Communications Server 2007 R2, Unified Communications Managed API 2.0 Core Redist 64-bit: May 2010

Download:
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=b3b02475-150c-41fa-844a-c10a517040f4