Mac OS X El Capitan, 4GB RAM, Optifine, recently upped allocated RAM to Minecraft to 3GB. Started having problems a few weeks later.

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I have been playing Minecraft with Optifine (no other mods) and experimenting with singleplayer worlds and getting on a server for a while now, and I have never had a problem. However, a few says ago, while I was loading new terrain, the rendering suddenly became very glitchy, with chunks appearing and disappearing everywhere. I decided to stop for the day.

The next day, I started the game and noticed music playing, which was puzzling because I always have the music turned off. I checked my settings and noticed that they were all reset to defaults. I ignored this and went to the singleplayer menu where I clicked the "Re-Create" button to re-create a singleplayer world (what I was about to do the previous day when I started having problems), and suddenly the game crashed and the launcher opened with a general crash message. When I tried to play the game again, it just crashed again. I closed the launcher and reopened it, and upon opening, I got the message

"A fatal error has occurred for unknown reasons. You may attempt to play the default game with default settings, but some functionality may not work (such as changing settings and remembering users)."

and the launcher was at the login screen, with none of my login information remembered. When I typed it in again and logged in, the normal launcher appeared, but with no options under the PLAY button. Just a button that says "PLAY" and nothing else, no arrow like there was before. I pressed play and everything seemed normal, except for my settings not being remembered.

Since I was finally able to get back on Singleplayer, I started playing, but just a half hour or so ago (a couple days after the problem started), the chunks in the world started corrupting themselves while I was playing it. Without saving and closing the world or anything, I started walking around and as previously-loaded chunks appeared again, a few chunks began appearing in the wrong places!

As you can see, I was experimenting with building a road when the problem started. I walked back onto the section of road I had just built, and boom.

I tried to take multiple screenshots, but my Mac began doing something else it had never done before: I had no permission to save screenshots. When I tried to take one, I got an error saying that I had no permission to save them. (Now, with the Minecraft client closed, I seem to have permission again.) I then tried to take them using the F2 key, but I only got one before it started giving me assorted errors including "null".

The only reason I can think of that these problems are happening is that a few weeks ago, when I had Optifine installed, I increased Minecraft's allocated RAM to 3GB, and my computer only has 4GB. Could this have been too much? Optifine hasn't been working since the first crash I had, when it seemed to have been uninstalled or no longer recognized.


I found the chunk that used to be here at another location nearby, with the section of road still going across it.

Please help me! What should I do to get Minecraft back to normal? Is there too much allocated RAM?