UPDATED 18.05.2014: Official information from Microsoft and workaround

More info here:

http://blogs.technet.com/b/servicemanager/archive/2014/04/23/update-rollup-2-for-system-center-2012-r2-service-manager-is-now-available.aspx

*** NOTE if you’re using SCCM Connector to synchronize data between SM and CM, do not install this Update Rollup (UR). We have discovered a regression in the UR payload which prevents the SCCM connector from successfully synchronizing in some cases. We expect a hotfix and / or the relevant documentation addressing this issue to be available very soon. Stay tuned for more information ***