Plutonium

Hi, recently a friend of mine upgraded his computer and added a 4GB RAM stick, however, after that, when he went to join a game, the game simply did not want to load the game, and when he enters it says that his connection was lost, but I went to test it on mine and it is loading the game normally, could it be this change from 4GB to 8GB, since the RAM sticks he is using on his computer are not the same, or was it something else, anyway, I count on your help