RK is correct. Good practice, regardless if it Civil 3D or AutoCAD, is to try to bit jump back and forth between versions. The potential prooblems are numerous. If you need to send your Civil 3D drawing back to earlier versions (even between 2014 and 2013) then it appears you need to return to old faithful: http://enceptia.com/dirt/?p=1717. It's not pretty, but it works. Try to remain in one version if at all possible.
Jason Porter Enceptia Technical Advisor & Civil Solutions Blogger http://enceptia.com/author/jporter/