“Add videos and photos” black screen glitch

Hi, I've been using Movie Maker for my youtube channel and it's a great program to edit my gaming videos.   I copied a video I recorded to my usb and put it onto my computer, and then load it into movie maker like any other time.    I did this yesterday and when I loaded it into Movie Maker it came up as if I just uploaded a black screen picture, and the duration is 7 seconds, instead of loading my video clip.  When I go to "Video Tools" it shows speed as if it's a video though.   If anyone could help me, I would really appriciate it as I can't make my video for my channel, and this will mess up my schedule.    Thank you.