Whenever I try to join a multiplayer game (servers, LAN, etc.) the game crashes and says "Authentication Error With Minecraft.net". I do have a minecraft.net account (verified and accessible) and the forums have no answers. My IGN is the same as my profile name. There is no issue with the launcher, nor with the authentication servers, but yet I am unable to join.

I have seen others with this problem and their own servers, but none of them have been fixed yet.

UPDATE: The client no longer crashes, but does prevent me from going onto any multiplayer service whatsoever. Even Realms doesn't allow me to access it.

UPDATE AGAIN: I have a vanilla launcher and game system. There are no mods or plugins on my computer that could alter the game, launcher or its code.
Please comment again if you would like my source code or something from the game to examine it.