Micrsoft have released Download details: Update Rollup 1 for Exchange Server 2007 Service Pack 1 (KB945684). From the download page:

Update Rollup 1 for Exchange Server 2007 Service Pack 1 (SP1) resolves issues that were found in Exchange Server 2007 SP1 since the software was released. This update rollup is highly recommended for all Exchange Server 2007 SP1 customers.

For a list of changes that are included in this update rollup, see KB945684.

This update rollup does not apply to Exchange Server 2007 Release To Manufacturing (RTM). For a list of update rollups applicable to Exchange Server 2007 RTM, refer to the section Update rollups for Exchange Server 2007 RTM in the Knowledge Base article KB937052.


Also, note this Technet article: Issues with Update Rollups.

Joe