If AutoCAD crashes when working with a specific drawing, the file may be corrupt (see How to Repair Damaged AutoCAD Files and Solving Poor Performance Problems with Specific Drawings in AutoCAD). The root cause of a significant number of Civil 3D problems that I solve comes down to the structure of the data. A poor data structure will cause Civil 3D to REGENERATE too much, and when Civil 3D Regens too much, it likes to fail. When you exit AutoCAD and log back in, you should expect to see the Drawing Recovery Manager.
If you don't see the administrator, you can open it by typing DRAWINGRECOVERY. When you close AutoCAD it's the same as when you turn off Windows and it goes and cleans some files before leaving to save space on your hard drive. For detailed information on what to do when AutoCAD doesn't start, see the official Autodesk solution for freezing or blocking AutoCAD. When you start AutoCAD or open a drawing, it crashes, crashes, or is generally slow or unresponsive.
DWG, rename the file to something other than the original and open it in AutoCAD.
