i have been trying to solve this problem for nearly 6 months. i figured it out. xbox live kept booting me out of games because there was a problem with my disk. my halo 3 had scratches on it and wasnt allowing me to load maps that are on the disk. i could only play downloaded maps. any time a match would be getting ready to start on a map i was having a problem loaded, i would get booted out. i had to buy a new disk. hope this helps