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Dear Mondi,
I was able to track down the reports you sent in. From the repors data it appears that you are running Civil 3D on Windows 8. Unfortunatley Windows 8 is not supported for Civil 3D 2013 at this time.
Only Civil 3D 2014 is supported on Windows 8. If you wish to keep running the 2013 release of Civil 3D you should roll back to Windows 7.
Kind regards,
Klaus
You can also find additional and updated information on Windows 8 support of Autodesk software at the following location:
Autodesk products with Windows 8 support