If you're playing on 14w34c, then that is the problem. It's a bug with the snapshot. Most likely, it's already been reported and Mojang is working to fix it as we speak.
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PC specs: Intel Core 2 Duo e8500 @ 3.16ghz / XFX Radeon HD 6670 2GB DDR3 / 6GB 1666MHz DDR3 RAM / Windows 7 Professional
PC specs: Intel Core 2 Duo e8500 @ 3.16ghz / XFX Radeon HD 6670 2GB DDR3 / 6GB 1666MHz DDR3 RAM / Windows 7 Professional