Do not use SAVE AS 2007 to save back a Civil 3D 2012 drawing and try to use it in AutoCAD or Land Desktop 2009. The drawing seems to work in 2007, but in 2009 basic editing fuctions are lost. Received erors inserting blocks, copy and paste command.
Had to Wblock the drawing to remove errors. (Recover and audit couldn't repair the problem)
Instead of SAVE AS use Export to AuotoCAD dwg.