Microsoft has released Update Rollup 3 for Exchange Server 2007 Service Pack 2, which resolves issues that were found in Exchange Server 2007 SP2 since the software was released. This update rollup is highly recommended for all Exchange Server 2007 SP2 customers.

This is a cumulative update and replaces update rollup 1 and 2. This update cannot be installed if you are using Exchange Server 2007 RTM or Exchange Server 2007 SP1. Any interim updates (custom fix from Microsoft Support) for Exchange Server 2007 must be uninstalled prior to installing this update rollup.

The list of fixes are detailed here

Download the rollup here

http://www.howexchangeworks.com/2010/03/update-rollup-3-for-exchange-2007-sp2.html