The Exchange Team has posted some disturbing information.
Over the weekend, the Exchange Product Group was made aware of an issue which may lead to database corruption if you are running Exchange 2007 Service Pack 3 with Update Rollup 3 (Exchange 2007 SP3 RU3). Specifically, the issue was introduced in Exchange 2007 SP3 RU3 by a change in how the database is grown during transaction log replay when new data is written to the database file and there are no available free pages to be consumed.
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.