After the latest debacle from Microsoft where Exchange 2010 SP2 UR5 got pulled due to a bug, Microsoft re-released the UR as version 2.
For more information on the UR, have a look at the following KB-article: http://support.microsoft.com/?kbid=2785908
However, I would wait a few more days (even weeks) before deploying this update. It’s not that I do not trust Microsoft or the Exchange Product Group, but – for once – I’d like to make sure we’re not running into any other unexpected issues. After all, Microsoft has had a bad track record with the stream of latest Update Rollups of which some even had to be pulled more than once.
Additionally, make sure to read Tony Redmond’s blog on this subject. There’s an interesting analysis of the different fixes as well as some other thoughts worth reading through:
Note next to Exchange 2010 SP2 UR5, Microsoft also released UR9 for Exchange 2007 SP3 (http://www.microsoft.com/en-us/download/details.aspx?id=36016) and UR7 v3 for Exchange 2010 SP1 (http://www.microsoft.com/en-us/download/details.aspx?id=35739)
Read the original announcement from the Exchange product team here: http://blogs.technet.com/b/exchange/archive/2012/12/11/released-update-rollup-5-v2-for-exchange-2010-sp2-exchange-2010-sp1-ru8-and-exchange-2007-sp3-ru9.aspx