IMovie 09

Hi I have iMovie 09 and I am in the process of editing gopro footage from the gopro Hero 3 Black Edition. However when I imported all the videos from iPhoto they are all visibe in the screen at the bottom right hand corner however when I select a segment and press the space bar to play them before editing no image appears but I ca hear the noises from the video clip? When I select a section and place it in the project window I can play it and see the video but I need to be able to see the video before deciding whether to use it in my movie or not. When taking videos with my other camera this did not happen could it be that the footage on the new go pro is too high resolution?

Thanks for your help.