Failure to launch - OS X 10.6.8

On launch, when using the "Play" button, the launcher instead restarts and yields the following game output:

Exception in thread "main" java.lang.NoClassDefFoundError: com/google/common/util/concurrent/ListenableFuture
at net.minecraft.client.main.Main.main(SourceFile:41)
Caused by: java.lang.ClassNotFoundException: com.google.common.util.concurrent.ListenableFuture
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 1 more