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.

Step 1:

Enter the game and select "Account & Network" - "Activision Account" - "Change Display Name".

Step 2:

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!