I have searched for a fix for this countless times. I cannot stress enough just how correct my username and password is. They are are letter for letter, capital for capital, 100% minecraft.net credentials, NOT WORLDOFMINECRAFT CREDENTIALS. When I try and connect to a server with a url it bring me to single player. In the CMD it gives me the warning 'WARNING: Found unknown Windows Version: Windows Vista'. I seriously need help on how to get this working.