Alright as many of you may already know if you are playing MW3 on the Pc and recently purchased the DLC there are some errors going around that say "Files different from server" this is due to an update server with the MW3 PC servers. I have found a fix regarding this and this should help solve any issues.
After it completes ensure that the Userdata folder has repopulated and then have them try to recreate the error
- Select My computer
- Select the hard drive the game is on
- Select Program Files
- Then Slect the Steam Folder
- From here move the Userdata folder to the desktop
- Then have the customer go to the steam client
- Right click the MW3 Multiplayer .exe and select properties
- Select the Local Files Tab
- Then select the Verify Integrity of Game Cache option
After it completes ensure that the Userdata folder has repopulated and then have them try to recreate the error
