GloW_iNg , ¿has probado de cambiarle el nombre al HDMI por PC como comentan aquí?
The Official LG LW450U 3D LED Thread | AVForums.com - UK Online
"Hi guys, seem to have solved the 360 lag issue I was having with COD Black Ops.
A guy on the AVS forum stated he had his PC connected through HDMI and was suffering lag with mouse movement, so he labelled the input as PC and the issue went away.

Worth a try I thought, so changed the 3rd HDMI input label from game to PC and voila.....movement feels normal again. Why does it work? No idea, but it does. I noticed it and asked my sister and her boyfriend (who has the sensitivity up to 10) to test it and they said it had gone too.

Just got to get better at the game now, and get the backlight issue sorted, and I have a near perfect TV. "