Class Version Error?

First time installing plugins and permissions and it gave me this error:

Code:

16:55:32 [SEVERE] Could not load 'plugins/Permissions.jar' in folder 'plugins':
java.lang.UnsupportedClassVersionError: Bad version number in .class file
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:676)
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
    at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:36)
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:24)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:317)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:375)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:242)
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:134)
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:160)
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:108)
    at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:85)
    at net.minecraft.server.MinecraftServer.e(MinecraftServer.java:217)
    at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:204)
    at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:144)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:259)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:394)

I have re downloaded the permissions .jar for 740 and redownloaded bukkit 740
I don't know if it is the version error because I have Essentials installed and they work fine.
Any help?