Unrelated problem, but Op1, Mission 3 doesn't want to end for me.
Is that the one with the crazy looking black structures that have the pop up turrets? If so you need to destroy those, hit the pillars themselves, there's three per set of buildings and each needs to come down.
If that isn't the mission I'm thinking of.. blame my lack of memory lol.
I really need to find my MW3 disc... I found my Pirates Moon one...