Btw i had this do it might be because you have to much mods and the texure pack it always happens to me try to force update and get the mods back if that does not work i can't tell you anything else but get a new minecraft.
Well the best thing to do is rather Re type your username and password if that does not work then in that case get a new account because it keeps happening to me but when i re type everything it's better.
Well i was happy that you can change gamemode even when you are in survival it's just I been waiting for enchatments i mean think about how fun that would be.
