NightRiderBEST

Hey guys I have a problem were every time I try to launch b team, Voltz, Tekkit, and all the rest it opens in the mojang screen loads a while then opens (after 2 hours) then when I click on singleplayer or multiplayer it crashes and goes back to the launcher. I have the memory set to 2 gb and I have 64 bit java anyone who can help that would be GREAT