I recently have found this issue as well. Here's the strange thing. I can't download videos from the content library into my in-process module, but I can download other media types to it such as images or icons, and if I open a NEW module I'm able to download the videos into a slide that do not work in the presentation I'm working on.
My previous fix was to copy all of my content from the presentation into a "new" module, which worked for a while, allowing me to download videos again, and is now giving me the issue again. Any ideas?
Thanks!