For anyone who still doesn't know how to freeze jump....
You need 2 controllers and a modded gamertag.

1st: You start a private match or a public one with your normal profile. (on controller 1)
2nd: You turn on your second controller and sign into a modded gamertag.
3rd: Now when you press backspace a error message will pop up. (on controller 1)
4th: You can do your freeze glitch now!
IMPORTANT! To do this more then once you need to repeat step 2. (signout and back in)