I know some people said to change to windowed full screen, I personally haven't had this issue but usually running this command for me with COD games usually helps with tabbing in/out.
r_fullscreen 0; vid_xpos 0; vid_ypos 0; r_noborder 1; vid_restart.
(Make sure to restart your game for it to take effect)
This is like "True" windowed fullscreen, also are you playing on plutonium servers or LAN mode?
undefined
