A hotfix has been released that improves Revit (all types) 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 (this can be found from the HELP pulldown (the question mark – ?) and selecting on ABOUT).
NOTE: This hotfix applies to the 64-Bit release of Autodesk Revit 2012 only.