Okay, so I set up port forwarding to play some Private Matches with the boys, problem is trying to load into a match results in this "file sum/name mismatch" error. I've tried searching the forums but have found no answers. I tried validating the integrity of the dedicated server tool in steam, but the problem persists. I tried relocating the file directory within the launcher, but the problem persists.
I do not own the full version of MW3 on steam, and am simply using the Dedicated Server Tool.