000513 : Unable to open <value>
The CAD file is not accessible to the Import From CAD tool. The CAD file may be in an unusable format or is not actually in the specified input location.
Ensure that the file is actually in the location specified. Another possible solution is to preview the CAD file in ArcGIS using ArcCatalog. If it is not viewable, re-save it in the CAD host it was created.