So your intrepid author spent the best part of his day undoing another fine mess by Microsoft!
Microsoft released Rollup 8 for Exchange 2010 SP3 as described here http://blogs.technet.com/b/exchange/archive/2014/12/09/exchange-releases-december-2014.aspx
After beginning deployment to our environment we found issues where our users couldn't connect properly to Exchange from Outlook, especially those connected Online (not cached mode). Users experienced errors such as 'Outlook cannot display this item' in preview pane, sub folders not showing messages, secondary mailboxes becoming inaccessible and messages lost mid composition and not even saved to drafts.
Just an immensely frustrating day of making various alterations to our servers, then after pulling back Rollup 8 service slowly began to normalise. Finally Microsoft updated their blog posting above admitting that there was a problem after all! (thanks for that).
If you have been lucky enough to be given this early seasonal gift then to remove Exchange 2010 SP3 Rollup 8 simply remove it from Installed Updates in Windows Update.
This is becoming an all too common occurrence now, Microsoft release patches and then pull them frustrating us and our clients as we have to pick apart the mess they seem to cause.
Meanwhile looks like another separate update has toasted 2008 R2...but enough challenges for one day!