A few weeks ago Microsoft released Update Rollup 5 for Exchange Server 2010 SP2 (link is currently not working, read on).
Normally these releases are accompanied by an announcement on the Exchange Team Blog, but this time there was no announcement, though plenty of MVPs and other bloggers immediately wrote about it.
Unfortunately it now appears there was a bug in this latest update. To the best of my knowledge this was first reported on Tony Redmond's blog via a reader comment, prompting Tony to recommend that people do not deploy it.
DO NOT DEPLOY RU5. Microsoft has been informed about a bug that affects DAGs. DO NOT DEPLOY RU5 until the bug is fixed! This proves once again that you should never rush a roll-up update into production. Always test, test, and test again first…
Now it seems the update has been withdrawn completely. The download link no longer works, and a Microsoft PFE commented in the TechNet forums:
It was removed due to an issue with the update – sorry!
Due to the bugs, and the fact that the update is now withdrawn, if you happen to have downloaded it while it was still available the sensible course of action would be to not deploy it in your environment.