Minecraft crashing at world load or server join.

I don't know if this is an issue for anyone else but I thought I would post a possible solution here in the event anyone experiences something similar.

Earlier today Mojang made some changes to their back end authentication code, (I'm guessing anyway,) in response to a server crashing exploit being publicly posted.  This appears to have broken some things and at least one mod, Optifine.  On 1.7.10 clients, and maybe other versions as well, Optifine is somehow interfering with Player authorization via Mojang so the client crashes on world load or server join. 

For Vanilla and Bukkit users experiencing this problem, disabling Optifine should stop the crashing.  For Modded players you may need to remove Optifine from the 'mods" folder entirely, because some mods, (Ars Magica,) optimize themselves for Optifine if it is present.  Some of those same mods, (Ars Magica,) stupidly scan the "mods" folder looking for a file containing the word "Optifine" in its file name and enable their support if they find it, whether it is loaded into the game or not. 

As I said, I do not know if this problem affects any version other than 1.7.10, but it might.  I only encountered the problem because I was working on the 1.7.10 Pack earlier, and between one launch and the next it started crashing and nothing had changed.


  • It looks like Optifine for 1.7.10 has been updated, so the problem is now solved.
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