How to reconstruct the incident:
0.0001. Don't throw salt over your shoulder before starting this, might give you good luck. Don't want that here. Yeah talking to you leprechaun!
1. Start up your brand new clean Minecraft version 15w32a client side game.
2. Go and create a new world.
3. Wait five minutes and wonder why hasn't anything happened yet.
4. Look at the new folder in your Minecraft directory: crash-reports.

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Now seems how you reconstructed the issue(don't wait five minutes, the server will have crashed long before then) I attempted to create a Creative Game Mode World in Minecraft, then it stopped working and I tried to close Minecraft a few times. I had to kill it with the Windows Task Manager, it was brutal. Bloody thing would not go down without a fight. Anyway, here is a JIT(Just In Time) log that Minecraft shown me. I didn't see someone else reported this bug today, sorry! But what they forgot was the crash log.