Very odd, my file was a .mov I believe. Are you using any form of compression? This particular .mov was compressed with .H264 but I raised the gamma slightly to compensate for the crushing of the black tones that usually occurs in that format.
An animation or film is submitted in the same fashion as any other deviation. As far as the category is concerned, the category itself is called "Film & Animation" and should be available about 1/3 the way down the category list.