Hi Amber,
I upload a 5 - 10 minute video to YouTube every week - couple hundred up there now. I have had a couple problems like yours in the past year. Have no idea what the problems were - each time the video "uploaded" and then a message came saying it didn't work, try again. In one case it took 5 tries. However, the problem has been very infrequent. If you have already tried several times, you might consider re-rendering the video and re-exporting it before uploading again.
Good luck,
David