Replying to Ipod help.

Ok I have a 5th gen. ipod video. I just bought a movie from the itunes store and it works on my mac, and when i open the ipod folder and click on the movie there it works. When I eject my Ipod and try to play said movie it shows the normal play start up stuff but then the screen is black and after about ten to fifteen seconds it goes back to the video home page. I have reloaded the movie on to the ipod four or five times now. CAN ANYONE HELP ME?