Update 7/4/2011 – Microsoft has now reissued the update rollup.
Microsoft has withdrawn the recently released Exchange Server 2010 SP1 Update Rollup 3 due to duplicate message problems reported by Blackberry customers.
We have received notification of an issue impacting some customers which have RIM BlackBerry devices connecting to an Exchange 2010 SP1 RU3 environment. At this stage we are actively working with RIM to identify the exact scenarios in which customers are reporting this issue in order to narrow down the root cause of the problem and identify a suitable resolution for it.
As a precautionary measure we have deactivated the download page for Exchange 2010 SP1 RU3 until we can identify the appropriate next steps.
More information is available here.