I have also had this a few times but its normally late at night and only playing against people in the US (I'm in the UK).

It as really annoying as a friend and myself were going for a perfect week in terms of wins (playing face off) and we were soooo close but then this happened then happened again and again and again........ Needless to say the Xbox got turned off.

I was getting dropped from games a lot, maybe 1 out of 4. I had my router port-forwarded to the Blops ports and my NAT type was Moderate. I got a new phone and couldn't remember my router password so I had to reset my router and I port forwarded it to the MW3 ports. Now my NAT type is open and I hardly ever get dropped from games. I doubt this will help but this was my experience.

I used to be doubtful that your router/xbox settings would affect your online play but I was 100% wrong.

I have been having this same problem constantly I am getting pretty fed up with it too and i dont use no gay lag switch and dang sure dont know how to change settings on a router or modem so if anyone has any information that could help out i would greatly appreciate it