I have had alot of issues as well after updating to patch 1.17 for the ps3 version. It's the game that is having major issues at the moment. I played 5 matches and got booted EVERY single time (DISCONNECTED FROM HOST). I was in the lead as well every match on FFA. Every match starts ok at first and then the lag quickly kicks in. Then things become SUPER LAGGY and then it freezes, goes black and I am back at the lobby with an error message.
I stopped playing after the 5th time it did that and started to watch Netflix.
The only anwser to your problem is...
1. Check your modem and/or router to make sure they are correctly connected and all lights are showing up. (CHECKED ALL MY EQUIPMENT AND IT WAS FINE)
2. Wait for Activision to put out a WORKING patch that is NOT programmed by a team of lazy, over paid chimpanzees. (NEVER TRUST THEM...EVER SEE PLANET OF THE APES?)
3. Take your copy of Modern Warfare 3 and send it into space on an exposlive rocket. Maybe the rocket will fail and take out Activision with it...=)
I don't know about you but, I am leaning towards option number 3 myself.