Played last night Europe only with a couple of yanks with me and NO lag and ps3 didn't freeze. Had a few issues initially hooking up together with invites but once we found the best 'host' game ran best it has for a while.
Try deleting all messages, disable multi media player in settings and delete friends you ain't played with in a while. If you still freezing look up YouTube, my ps3 is 5yrs old can't remember the spec. Good luck.
A support case was created for you and you should be contacted shortly by a Customer Support Representative, if you haven't been already. You can view and update your case at the Activision Support website. After logging in, go to "My Support" then "My Cases".