Okay, found the issue and resolved it. I installed X-Plane from the DVD 1 installer, which is apparently not a good idea (I know now LOL), so I donloaded the installer/updater, and just to be sure I also re-downloaded the DC-3 (although I suspect that was not necessary). The downloader updated Z-Plane 10 and then I uninstalled and reinstalled the DC-3 and it was working. So, it seems that installing from the DVD 1 installer is the issue. Thanks for the help incidentally. Al