Exchange 2010 SP1 Update Rollup 4 released
for download here
For those of you running Forefront Security for Exchange, disable ForeFront by using this command: fscutility /disable, before you install this update. After installing the update, re-enable ForeFront by running fscutility /enable.
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.