I purchased Black Ops 2 on Friday, and experienced a hard freeze during the first mission. (At the checkpoint where you hide under the log before the radio tower.)

After two or three restores, I knew it was the game and not the HDD because it always froze at the same bit. Which was annoying because I was enjoying the campaign up until that point.

I was ready to take it back to the shop, and put it to one side.Last night, I loaded it up again just to see if the same glitch would happen during zombies. The session worked fine, and I went back to the campaign.

This time, I saved and quit after each checkpoint and then resumed the campaign. I wasn't sure if it would help at all, but tried anyway. When it came to the scene with the kids and guard, I waited for the freeze but it never happened.

The checkpoint saved and I haven't had any more problems since.