If you are prompted that loss of connection to the host during gameplay in MW3, then please refer to the following steps to fix the issue.
Enter the game and select "Account & Network" - "Activision Account" - "Change Display Name".
Go to Activision's official website, choose to log in, after logging in to your account you will be asked to enter your name again, when you are done, re-enter the game and you are done!