if you set all of performance options on zero , it will happen. It makes fps drop + lag on your side. If you get a updated and a powerfull laphtop/Desktop. Fps drop fades. But Lag stays the same. Try to set all graphical options on high. But stay at 800 *600 or higher. And disable 3D audio in option.
If you did these all befor the lag, well....i dont know more.
