Can't launch game

[freddie11234]

I've recently tried installing optifine, hoping it would boost my FPS enough to enjoy the wonders of Hexxit. After I installed it and tried to run Hexxit, it wouldn't finish launching. The button says "Launching..." and then it just sits there. I've left it open for a while thinking it would eventually start up, but it hasn't. Am I doing something wrong, or can anyone help me correctly install optifine? I was following this tutorial if that helps with anything.

Here's the error in console when I press the "Launch" button.

org.spoutcraft.launcher.exceptions.UnknownMinecraftException

    at org.spoutcraft.launcher.launch.MinecraftLauncher.getMinecraftApplet(MinecraftLauncher.java:99)

    at org.spoutcraft.launcher.GameLauncher.runGame(GameLauncher.java:133)

    at org.spoutcraft.launcher.GameUpdater.runGame(GameUpdater.java:81)

    at org.spoutcraft.launcher.skin.LoginFrame.onEvent(LoginFrame.java:300)

    at org.spoutcraft.launcher.skin.LoginWorker.doInBackground(LoginWorker.java:102)

    at org.jdesktop.swingworker.SwingWorker$1.call(Unknown Source)

    at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)

    at java.util.concurrent.FutureTask.run(Unknown Source)

    at org.jdesktop.swingworker.SwingWorker.run(Unknown Source)

    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

    at java.lang.Thread.run(Unknown Source)

Caused by: java.lang.NoClassDefFoundError: aca

    at java.lang.ClassLoader.defineClass1(Native Method)

    at java.lang.ClassLoader.defineClass(Unknown Source)

    at java.security.SecureClassLoader.defineClass(Unknown Source)

    at org.spoutcraft.launcher.launch.MinecraftClassLoader.findClassInjar(MinecraftClassLoader.java:169)

    at org.spoutcraft.launcher.launch.MinecraftClassLoader.findClass(MinecraftClassLoader.java:143)

    at java.lang.ClassLoader.loadClass(Unknown Source)

    at java.lang.ClassLoader.loadClass(Unknown Source)

    at java.lang.Class.getDeclaredFields0(Native Method)

    at java.lang.Class.privateGetDeclaredFields(Unknown Source)

    at java.lang.Class.getDeclaredFields(Unknown Source)

    at org.spoutcraft.launcher.launch.MinecraftLauncher.setMinecraftDirectory(MinecraftLauncher.java:111)

    at org.spoutcraft.launcher.launch.MinecraftLauncher.getMinecraftApplet(MinecraftLauncher.java:86)

    ... 11 more

Caused by: java.lang.ClassNotFoundException: aca

    at java.net.URLClassLoader$1.run(Unknown Source)

    at java.net.URLClassLoader$1.run(Unknown Source)

    at java.security.AccessController.doPrivileged(Native Method)

    at java.net.URLClassLoader.findClass(Unknown Source)

    at org.spoutcraft.launcher.launch.MinecraftClassLoader.findClass(MinecraftClassLoader.java:149)

    at java.lang.ClassLoader.loadClass(Unknown Source)

    at java.lang.ClassLoader.loadClass(Unknown Source)

    ... 23 more