Game will not start

I'm currently having trouble with my game. For some reason, it will not start anymore. I played it two times before. Once with no resource packs, and another time with a resource pack. But after that, the game stopped launching. The loading bar gets stuck at about 95%. When I remove the resource pack from the folder, there is no loading bar at all; just a white screen. The only way to actually play the game is to use the old launcher, but then I have no skin.