Dirty disc error with halo 3 on the xbox 360

Alright chaps hope all is well!

wednesday the 17th of october i purchased a new copy of halo 3,

despratly wanting to play it i confinced my wife to go to bed early so i could get a good few hours of heavy slaughter under my belt.

getting past the first intro screen the game crashed and came up with an error telling me the disc was dirtyso i cleaned the disc with a soft cloth like it suggested and continued to load the game.

now this happened on a number of occasions during the night with not one minute of game play, so i took the game back and got it replaced with a new one.

so last night i tried the same, getting my miss,s to go to bed early so i could play the game, and so and behold the same sodding problem.

so i tried a number of my older titles with no problem at all.

pease help me!!!!!!!!!!!!!!!!!!!