I followed a tutorial exactly the same as that. My maps show up in the map menu. When I try to play a map, the screen goes black (like when normally loading a map), but it just returns to the pre game lobby or the main intro menu.
I have to say, it looks awesome. I just downloaded it, but I dont know what to do with it. I have no experience of modding halo. Could someone provide a link to a tutorial, or if it is simple just tell me what to do. (I have halo 2 on my HD). I have looked for ages, but I can't find any answers.