Halo 3 xbox 360. Unable to join user created content parties :S please help?

[Lauren J]

My friends create a custon game and they invite me to it,,
i then accept but,. when i accept it says you were unable to connect to .... because a member in your party is restricted from playing user created content.
the only member in my party is me, so it must be me.,
how do i change the settings so i can get acces to user created content???? thankyou heaps