A few Civil 3D users are getting errors and the quick exit out of Civil 3D when they try to export to ESRI shp format with Civil3D 2009. One thing they need to check is the mapexport.ini file located in the C:\Documents and Settings\All Users\Application Data\Autodesk\C3D 2009 folder. The ini file can be opened and edited in Notepad or any text editor. Look for a section called [SHP]
If it looks like the above then edit the value for EntType to Type instead of all.
So that it looks like this:
Save the changes and close the file. Now when you call the mapexport command in Civil 3D you will get the old dialog back that allows you to select the object types. You will need to select the object types (point, lines, polygon, or text) to export.
The reason the ALL value is causing errors is ALL = ALL to include the Civil 3d objects, and as we all know Civil3D objects do not play nice with Map3D. If you are still getting errors on the export review the post here and watch the file names or here for a little tip about exporting text.
Update for 2010 Civil 3D : Looks like the issue is in the 2010 version also.