"Roaming" directory error?

I have a presentation with some slides that I need to incorporate into another new presentation.  When i use the slide-sorter to select and copy the slides and I paste them in the new presentation the mp4 files don't play -- when I try and publish them nothing comes up and when I try and edit the video (in presenters) to make sure it's still there I get some sort of roaming error... see error message.

What is the proper way to copy slides with video from one presentation to another?

This also applies to slides with audio tracks.