This issue is of specific concern in two scenarios: 1) when transaction log replay is performed by the Replication Service as part of ensuring the passive database copy is up-to-date and/or 2) when a database is not cleanly shut down and recovery occurs.
While only a small number of customers have been affected to date, we believe the risk is significant enough that we are recommending all customers to uninstall Exchange 2007 SP3 RU3 on all Mailbox Servers and Transport servers. Uninstalling the rollup will revert the system back to the previously installed version. We have also removed the Exchange 2007 SP3 RU3 download from the Microsoft Download Center and from Microsoft Update until we are able to produce a new version of the rollup.
When this issue occurs, the following similar events are logged in the Application Event log of the Mailbox server. Regardless of whether you see these types of events, you should review the recovery instructions and begin that process. If you are uncomfortable performing any of these steps please contact Microsoft Support for assistance.
See the full article: http://blogs.technet.com/b/exchange/archive/2011/03/29/potential-for-database-corruption-as-a-result-of-installing-exchange-2007-sp3-ru3.aspx