How Come When I Try to Play Halo 3 Odst Matchmaking It Says I'm Not Connected to Xbox Live?

I AM connected to Xbox Live because I can play xbox live on other games and I'm signed into messenger.

So It says I'm not connected (only for halo) when I am… how do I fix it?

Suggestion:

the servers might be down. hey add me on xbox BLAZE LMTD EDTN