I keep getting a disc unreadable message for Halo Reach and Lost Planet 2. With Reach it's only during Multiplayer, usually directly after a match. With Lost Planet 2 it's kinda random but happens more frequently when I attempt to play a multiplayer game.
I've been able to play all of my othetr games with no problem. I've even tried playing after installing Reach to my HD (Lost Planet 2 was bought through games on demand so is on my HD already)
I'm using a 360 with a 20 gig HD