Yeah, that has happened to me on a few occasions. Let me track my steps for everyone else who may be interested in this. All five of you.
I first built my playlists in one giant folder called NCAA Sounds. I named every song/event with the school name_song title_event.mp3. Then I created a folder for each school within that giant folder. That helped me break things up.
After I got my mp3 files in order, I began building my m3u files library in each school folder. For my Alabama_Bammy Bound_FG.mp3 I created a Alabama_Bammy Bound_FG.m3u file in that same folder. The m3u file is simply a text file with the name of the mp3 inside of it saved with the extension m3u. I saved all of my files as Latin 1, which is a Windows codec for m3u. You can also add in directives to you m3u files, but I don't think that is necessary. Just remember that the text inside the file is mp3 and the text is saved as m3u.
So, got my mp3 and m3u library built in my NCAA Sounds folder, which I keep on an external hard drive. You don't have to do that. I do it because I don't need all of these files on my hard drive.
Here's is the tricky part that got me. If you are using Rivet or Connect360, you have to now build MORE playlists in iTunes. These program do not allow you to grab music files from just any old folder. I even tried switching my source folder for iTunes so that it would go to my external hard drive. That did not work for me. I also tried making an alias NCAA Sounds folder. Did not work either. So you're basically stuck using iTunes in this process as a middle man.
In building your playlists in iTunes, REMEMBER to load each song/event by clicking your m3u file. That is what tells iTunes where to get the file to play it. I screwed this up thinking I didn't need those m3u files I created and started clicking the mp3 files so they would play in iTunes. They won't even get to your 360 that way. I know there's a better xml script that would cut through all of this m3u nonsense, but I'm not versed in xml, which is the file type iTunes uses for its playlists.
So hit that m3u file, watch it load in iTunes and then save the track as a playlist. Load your one song/event per list and then truncate them into conference folders to reduce the eyesore in iTunes.
You can begin to check in with Rivet to see your playlists build. Just go to preferences, music and see all of your playlists listed. I only have music selected and the selected files option selected. NOTE, if you have an unchecked playlist in the middle of your event playlists, the game with stop playing the song/events after that point. Meaning, if you have playlist "A" and then playlist "B" is unchecked, playlist "C" will not play. You pretty much have to delete the playlists you don't want the game to see via iTunes. That or just stick an X in front of the title so it appears last on your Rivet preference plane.
Jeeez... what else? Once your iTunes lists are finished, close Rivet out and re-open it. Then go to your Xbox and start it up. Go to my Xbox, music library and saved playlists. Your playlists should be there. Test a few out because if they don't work here, they will not work in the game. If they work here, they should work in the game. Of course, as I type, mine are playing fine in the dashboard, but I'm getting error messages when I attempt to pull them up in the game. If only some work, check back on the unchecked playlist issue or the method in which you loaded each event into iTunes.
mtoo22, your issue is the same as mine. I'm still trying to figure out why the game recognizes files one minute and not the next. Why do the files play clearly in the media center, yet lag and freeze the game at times? I don't know. It's been a lot of trial and error for me. It was worked perfectly on occasion. I had Alabama playing home against Tennessee and the atmosphere was improved 100-fold with Stadium Sounds added. There's a lot of dead air in this year's game that needs to be filled.
I'll keep checking in with anything I figure out. Please do the same.