DXtory Crashes COD4

[Col. Mustard]

I ran DXtory and then started COD4 and when then I get a iw3mp.exe error which is the multiplayer exe and the game shuts down. I then exited DXtory and restarted the game. It then works fine. I then minimize the game so it is still running and start DXtory and my game crashes with the iw3mp.exe error again. What could be causing this?