Loading screen doesn't convert to game screen

Loading screen hits 100%, game starts, game screen won't appear. I use mac client. Just got a new modem, internet works great, But I either load in 3 minutes late into the game (hurting my team) or I have to restart league which says I then disconnect and then connect properly. So I reconnect, load in, and everything is fine. The only catch is my friends are on Skype with me, and they tell me I've loaded in. they see me in game, but i'll get an AFK warning from leaver-buster if I take too long to load in. (because it crashed) I am kind of scared to do ranked because of this bug. Please help in any way you can!