I occasionally hit this huge lag spike from no where, another friend has this issue also and yes his disc is also installed. It's not my connection, I already know that's the first thing that's pinpointed. But it's the fact this lag hits in single player as well, so I'm 100% positive it's not the connection. It's just kind of irritating since it hits at the worst time, usually during a firefight or on a killstreak that I'd rather not have ended but get instant killed once it starts up.