This week Autodesk released a Hotfix for all 64bit Revit applications.
This hotfix improves product stability when working with large datasets.Make sure that Update Release 2 has been applied prior to adding the hotfix. Verify that the build number of Revit 2012 is 20110916_2132. NOTE: This hotfix applies to the 64-Bit release of Autodesk Revit 2012 only. Read me