Del site del Team de Exchange
"Earlier today the Exchange CXP team released an updated version of Update Rollup 4 for Exchange Server 2010 SP1 to the Download Center. This updated release is being made available after a complete review and revalidation of the list of fixes included in the previously released version of Rollup 4 dated June 22, 2011.
The review completed by the Exchange CXP team determined that the issue identified in 'KB 2581545: The copy or move operation on a folder that contains subfolders does not work as expected after you install Update Rollup 4 for Exchange Server 2010 SP1 dated June 22, 2011’ introduced a serious regression in the original release of Rollup 4. As a result, a new version of Rollup 4 dated July 23, 2011 has been tested and released with the change that caused the regression removed. The re-release of Rollup 4 is tracked by 'KB 2579150: Description of Update Rollup 4 for Exchange Server 2010 Service Pack 1'.
The updated Rollup 4 is being released to allow customers to install the list of fixes previously committed to on the normal rollup schedule using normal rollup installation routines without the need for further action. The re-released version of Rollup 4 is functionally equivalent to the combination of the original Rollup 4 release and (the interim updatein) KB 2581545. Here are answers to some install questions:
- Customers who have installed KB 2509910 (Rollup 4, dated June 22, 2011) and KB2581545 (fix for Rollup 4 regression) do not need to install KB 2579150 (re-released Rollup 4) but may do so if they choose to.
- Customers who have already installed KB 2581545 and want to update their systems to the updated Rollup 4 should first uninstall KB 2581545 (or any interim updates) prior to installing the new rollup.
- You do not need to uninstall original RU4 (KB 2509910) to install the re-released RU4 package (KB2579150).
- The re-release of Rollup 4 does not change the release plans for Update Rollup 5 for Exchange Server 2010 Service Pack 1. Rollup 5 is currently scheduled to release in August 2011.
Nota completa http://blogs.technet.com/b/exchange/archive/2011/07/27/announcing-the-re-release-of-exchange-2010-sp1-rollup-4.aspx