I have been working in Civil 3D 2013 for about two weeks and everything was going smooth until I got a fatal error message while trying to rotate a basic rectangle. When I reloaded AutoCAD Civil 3D my command line displayed the following error message: "AutoCAD menu utilities loaded.; error: bad argument type: input-streamp: nil”. My drawing loaded normally but when I tried to draw a line using L+Enter I got a note saying “Command: L Unknown command "L". Press F1 for help.” Now none of my aliases work and when I go to Express -> Tools -> Command Alias Editor from the menu bar, I get the windows that are on the attatched screen shot. The PGP files wont work and importing aliases gives me the top right box on the attatched image. I have tried adding a Support File Search Path from the options menu and that too has failed. Any suggestions as to what I can do?
Do a repair installation and I'm sure you'll be up and running in a few minutes.
That did work but do you have any clues as to what caused this error to prevent future occurrences?