Stupid problem.

Code:

Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(Unknown Source)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(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.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:41)
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:29)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:131)
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:285)
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:200)
    at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:156)
    at org.bukkit.craftbukkit.CraftServer.<init>(CraftServer.java:132)
    at net.minecraft.server.ServerConfigurationManager.<init>(ServerConfigurationManager.java:52)
    at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:148)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:408)
    at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)

This happens to ALL MY PLUGINS. Using eclipse.

Solved. Stupid java 7.

...Not solved. I set JRE and compiler to 1.7 and didn't work.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Run it in Java 6, You're running your server in Java6 not 7 , The way I set it is using the Java SE 1.7 environment