If you still have Exchange Server 2007 RTM the Rollup update #06 was released yesterday. This update can be found at http://www.microsoft.com/downloads/details.aspx?familyid=0b2993a3-d290-453e-85fe-108867865731&displaylang=en&tm
Please pay attention to the note section of the download page:
This update rollup does not apply to Exchange Server 2007 Service Pack (SP1). For a list of update rollups applicable to Exchange Server 2007 SP1, refer to the section Update rollups for Exchange Server 2007 Service Pack 1 in the Knowledge Base article KB937052.