Moving videos from iPhoto library within iMovie 10.0.4 to event

I am currently using iMovie 10.0.4. I would like to move some videos from my iPhoto Library (within iMovie) to a new event. I am able to click on the individual video clips, successfully highlighting them. However, when I try to drag each clip to the new event I have created, they do not move. I have tried to move them both to the library listing in the left margin and to the bottom half of the screen with no luck. What am I doing wrong? Thanks for your help.