Earlier today the Exchange CXP team released Update Rollup 5 for Exchange Server 2007 SP3 to the Download Center.
This update contains a number of customer-reported and internally found issues since the release of RU4. See 'KB 2602324: Description of Update Rollup 5 for Exchange Server 2007 Service Pack 3' for more details.
We would like to specifically call out the following fixes which are included in this release:
Note for Forefront users: For those of you running Forefront Security for Exchange, be sure you perform these important steps from the command line in the Forefront directory before and after this rollup's installation process. Without these steps, Exchange services for Information Store and Transport will not start after you apply this update. Before installing the update, disable ForeFront by using this command: fscutility /disable. After installing the update, re-enable ForeFront by running fscutility /enable.