The FILEDIA variable has a tendency of being set to zero when Civil 3D crashes. This results in your file open options being displayed on your command line. A major annoyance. This topic has been posted on the discussion groups several times. One solution is to place the following line in an acaddoc.lsp file in you civil 3d support directory.

(setvar “filedia” 1)

If you don’t have an acaddoc.lsp file you can create your own in notepad and save it in your support directory. Or right-click and save as the file here.

The acaddoc.lsp file is run by autocad when you open a new file. The line you added will set FILEDIA to 1 preventing the dialogs from being disabled.