I have the same problem resaving files with C3d items (old farm, stave church and corduoan lighthouse) and sent a ticket to their support. They just emailed me back this reply:

*"We have fixed a similar problem in our internal version, about resaving a scene containing copy-protected cornucopia3D items. Next update should sort things out. Thank you for your report."

The new update hasn't been posted yet (as of this post!).