Halo 3 ODST won't load

I bought the Halo 3 ODST yesterday, I downloaded and went to play it tonight and it wont the first mission. The bar just remains blank and unfilled, I deleted and re-installed ODST with the problem still persisting. I have tried loading different missions with the problem still continuing. I have no idea what is going on, the only other option I can think of is to re-install the entire game and quite frankly I really really don’t want to do that. I cost me around 6.95 which I know isn’t much in the grand scheme of this but I really want to play this campaign and it is incredibly frustrating paying for a product, waiting a night to download it (I live in Australia so my internet is about 1.5MB/s at max speed), plus waiting an entire day to play it as I am in school at the moment and now I cant even load the game. As I said before I have no idea why this is happening but if anyone on the forums or from 343i can assist in this issue I’ll be greatly appreciative.

Cheers