The Collection 4 DLC has what is I am sure is a reproducible bug on some consoles other than mine. 

If I download all 5 maps I cannot start the game anymore - it leaves the dashboard and the screen goes black but it appears to be stuck in a loop. If I go to my dash menu where "Play Modern Warfare 3" & the disc icon are, it repeatedly switches between enabled/disabled.

IF I go to my hard drive and remove any single map of the five new ones (it does not matter which), then I can load the game.  However I cannot play in the "collection 4" maps since I do not have all 5.

This is the message I get: "Playing with original maps only. download all DLC content you are entitled to from the STORE in order to play on DLC maps." Which leads me to believe that the Collection 4 is fully installed I cannot play on ANY of my PRIOR DLC maps.  I have not confirmed this but that's what the message says.  I did manage to load a game which was on the free-to-public map "Terminal". 

So this issue is pretty huge, and I'm sure there's got to be some others with this issue.  RECAP:

1. Collection 4 renders MW3 absolutely unplayable

2. Removing any one of the Collection 4 maps allows MW3 to load but the remaining maps of Collection 4 cannot be played, and possibly other collections are unplayable too.