Regular crashes when in Nether; invalid memory access

Game crashes very frequently while in the Nether. Makes it very hard, nearly impossible, to do anything.

Seems like hitting ESC directly on entry makes the crash a bit rarer, but it's no guarantee the game will continue to run normally.

This does not happen in the Overworld. Idk about the End, haven't been there yet.

Made a crashlog using instructions found at http://www.minecraftwiki.net/wiki/Crash#Mac_OSX

At the moment of the crash, log shows:

10/04/2013 01:41:25 [0x0-0x57c57c].com.Mojang Specifications.Minecraft.Minecraft[49196] Invalid memory access of location 0x7fc0351a7 rip=0x7fc0351a7
10/04/2013 01:41:36 com.apple.launchd[136] ([0x0-0x57c57c].com.Mojang Specifications.Minecraft.Minecraft[49196]) Exited abnormally: Bus error
10/04/2013 01:41:36 com.apple.launchd[136] ([0x0-0x57c57c].com.Mojang Specifications.Minecraft.Minecraft[49196]) Exited abnormally: Bus error

Invalid memory access. Must be a bug.

Rest of the log is fine, nothing unusual there. So no need to attach that. The crash comes out of the blue, with above error messages in Console.

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I tried searching for this, but all the Nether crash related issues are shut down and none of them speak of invalid memory access. That is why I believe this needs to be a new issue. Thank you.