Why won't Windows Live Movie Maker import my videos?

I used to be able to make videos in Windows Live Movie Maker but since a couple months ago, it just doesn't work anymore. It gives me that exclamation point sign where the video is supposed to be for ANY type of video I try to import (.avi, .mp4, .wmv., etc.) I've tried completely uninstalling all Windows Live Essentials including WLMM and reinstalling it but it still refuses to work. I'm completely befuddled and desperately need help fixing this since I love making videos. =\