MS Lag is the result of poor latency. Latency is the time it takes for your keystrokes to communicate to the server. For example, lil's 150ms would be on the high end of a playable latency.... (ms is milliseconds, if you were unaware.) I, being in Southern California, have around 130 ms on Aerie Peak, which is in New York, and less than 30 on servers based in Los Angeles, such as Korgath.
There is also FPS lag, which is a direct result of poor CPU performance. Average FPS, for a modern computer, on this 8 year old game should be over 60. I play on a 4 year old laptop, and maintain about 35, which is a totally tolerable number, but when I spike below 20, I find the game to be quite unplayable.