"Warning: An error occured during save" arises when saving a drawing which contains a style which was created with a layer from another "layer source" drawing.

1.  File new from _AutoCAD Civil 3D (Imperial) NCS Extended.dwt (drawing2.dwg) 2.  File new from acad.dwt (drawing3.dwg) 3.  Under toolspace/settings for drawing3.dwg, right click on General-Label Styles-Line and select New.
4.  General tab, left click on the box next to Layer that currently contains 0, then click on the ... to the right.
5.  Left click on Drawing3.dwg under Layer source at the top left of the Layer Selection dialog and select Drawing2.dwg.
6.  Select C-ANNO then OK and OK and save the drawing as temp.dwg.

This results in an AUTOCAD Message box with this text:

Warning:  An error occured during save.
We recommend that you run RECOVER on the drawing.

Workarounds:
... bring the layer into the new drawing prior to assigning it. ... This, unfortunately, negates the functionality of using "layer source".

Autodesk Service Request: SR#1-3608470141
Submitted By: TommieR
First Appeared: Civil 3D 200?
Status As of 2009: Still Reproducible