Notes: There is a common error that causes the game to not properly launch and gray out the "play" button. To fix this, delete your .minecraft folder. In order to know if you are affected by the error, a sample error is provided: ------------------------------------------------------------------------------------------ Job 'Version & Libraries' finished successfully Launching game Looking for old natives to clean up... Fatal error launching game. Report this to http://mojang.atlassian.net please! java.lang.NullPointerException at net.minecraft.launcher.GameLauncher.cleanOldNatives(GameLauncher.java:515) at net.minecraft.launcher.GameLauncher.launchGame(GameLauncher.java:360) at net.minecraft.launcher.GameLauncher.onDownloadJobFinished(GameLauncher.java:693) at net.minecraft.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:124) at net.minecraft.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:15) at net.minecraft.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:94) at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.util.concurrent.FutureTask.run(Unknown Source) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker. ------------------------------------------------------------------------------------------ .minecraft/minecraft folder locations: Windows =%appdata%\.minecraft Linux =~/.minecraft Mac OS X =~/Library/Application Support/minecraft