Try a repair install or delete the CascadeInfo.cas file and see if you have any luck.
For more detailed information about the CascadeInfo.cas file, please refer to the Autodesk Support Knowledge Base article found here:
For non-license related instances where your Autodesk product starts and hangs, please review this Autodesk KB on the InfoCenter:
I have seen this happen on our laptop.
This is my solution:
Try right clicking the AutoCAD Civil 3D icon on your windows desktop--> properties
In the Shortcut Tab, Target field look for "<<C3D_Imperial>>" at the end of the script. (your custom profile name might be here instead)
change it to "test". This will build a new profile.
Go to OPTIONS--> Profiles Tab and set "<<C3D_Imperial>>" current (or your custom profile name)
Unfortunately, this last step needs to be done every time Civil 3D is opened.
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