How To Stop lol Crashing?

I have recently started playing league of legends. I have also upgraded my computer since I have started playing. Often when i play my firewall gets in the way, McAfee, and I would like to know how to let McAfee allow lol. When i have chosen my champion and we are all about to load into the game is when it crashes if the firewall is left up normally. It also often crashes after the game so i cannot see the end game stats/talk to the other players. My friends who live in the same building do not have this problem, other than the one who also uses McAfee, leading us to think that is the cause, but we cannot find a solution