Posted by: lilstew12
Try clearing your Xbox's cache. It sometimes messes up Halo 3 MM.
Go to the Xbox Dashboard, select the System Tab, and select Memory.
Highlight the HD symbol and press Y.
Press X, X, Left Bumper, Right Bumper, X, X.
And then Up, Up, Down, Down, Left, Right, Left, Right, Select, Start for infinite lives.