FM 2012 - Game become so slow after Substitution when playing network game

Hi Guys, I hope you can help.

My game runs perfectly fine until match days when I go to make a sub or make tactical changes. Its slows the game down and takes ages to complete. I am getting to the stage where I do not want to make changes to avoid the game taking 10 mins to complete the last 30/20 mins of a game.

Btw, I am playing on a network game, my mates do not have this problem. Just me. I am also playing on a macbook.

Chris