I have been editing a wedding video for two weeks and have no had a problem until the last day. I went to add one last audio track and discovered that all video starting from the middle of the reception and everything after is a red box that says media offline in several languages. I have never had this problem with this or any other project. Why now? I have the project and video clips saved to an external hard drive and I filmed the video with a Canon 60D. Why is this happening? I'm using a new Dell Inspiror 15 with Windows 8 OS. I need help ASAP.