MauveCloud :
Alternatively, it might vary based on the server load. Does it give you any way of checking how many others are on the same server? If so, compare how many are on when you get 30 fps to how many are on when you get 120 fps. You could also try messaging other players to find out what frame rates they're getting. If the other players are getting the same frame rate you are, then it's a server issue rather than an issue with your rig.
Please stop. What you are saying is not how multiplayer gaming works. FPS is purely client side. Lag which has nothing to do with FPS involves communication issues between the client and the server.
http://en.wikipedia.org/wiki/Lag#Lag_in_online_multiplayer_gaming
In no way can the server limit the FPS rendered by the client's CPU and GPU. Depending on how the game was designed, the environment can be taxing on the computer. For example, the more people you are playing with, the more scenarios your components have to render.
Let me put it to you like this. You and I are playing chess over the phone. We each have a chess board in front of us. The communication over the phone, while very simplified, is basically how two computers communicate to a server. When a person makes a move, you lift your arm to move a chess piece on the board, which is your computer rendering the game. Explain to me how a break in communication affects how fast you lift your arm? It doesn't. You waiting for me to make a move has zero impact on how fast you lift your arm.
Yoplait, have you tried not playing the game in crossfire?