My MW3 keeps freezing in the middle of an online game. The disc is perfect and my internet connection is good, anyone know what is happening?
Even with a perfect-seeming disc and a good connection, it still sounds like you could be expriencing a broad range of issues. This Call of Duty Forum post is a really good place to try continuing troubleshooting your problem. The OP has a series of tests that they tried. (They still don't know what's happening, but they've at least eliminated all the major possibilities.) As another poster in that thread points out, once you've eliminated all major possibilities, you may want to contact a Sony Customer Support representative.
Let us know what you find out! The more solutions on the web, the better!