I was having the same problem. I was attempting to add an mp4 movie to my library and it just would not appear under movies. I did a search for the file name in the itunes search bar and my file appeared. It has been under the "Home Movies" sub header. This was changable from right clicking, selecting "get info" > Options tab and using the dropdown to select the media type and change it to movie. It then showed up in the place I was looking. I sort of feel dumb for having missed that, but hopefully this will save someone else that shameful fate.
Great!! Could have been the reinstallation that requires a restart to get it to work.!!