Server doesn't start

[Guest]

Whenever I try to load the server I get this error:

20:20:41 [SEVERE] A problem has occured during mod loading. Likely a corrupt jar is located in your mods directory
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20:20:41 [SEVERE] cpw.mods.fml.common.LoaderException: cpw.mods.fml.common.LoaderException: java.lang.UnsupportedClassVersionError: net/minecraft/server/mod_NetherOres : Unsupported major.minor version 51.0
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20:20:41 [SEVERE] at cpw.mods.fml.common.Loader.load(Loader.java:436)
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20:20:41 [SEVERE] at cpw.mods.fml.common.Loader.loadMods(Loader.java:606)
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20:20:41 [SEVERE] at cpw.mods.fml.server.FMLBukkitHandler.onPreLoad(FMLBukkitHandler.java:134)
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20:20:41 [SEVERE] at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:135)
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20:20:41 [SEVERE] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:438)
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20:20:41 [SEVERE] at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
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20:20:41 [SEVERE] Caused by: cpw.mods.fml.common.LoaderException: java.lang.UnsupportedClassVersionError: net/minecraft/server/mod_NetherOres : Unsupported major.minor version 51.0
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20:20:41 [SEVERE] at cpw.mods.fml.common.Loader.loadModClass(Loader.java:527)
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20:20:41 [SEVERE] at cpw.mods.fml.common.Loader.attemptFileLoad(Loader.java:562)
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20:20:41 [SEVERE] at cpw.mods.fml.common.Loader.load(Loader.java:419)
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20:20:41 [SEVERE] ... 5 more
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20:20:41 [SEVERE] Caused by: java.lang.UnsupportedClassVersionError: net/minecraft/server/mod_NetherOres : Unsupported major.minor version 51.0
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20:20:41 [SEVERE] at java.lang.ClassLoader.defineClass1(Native Method)
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20:20:41 [SEVERE] at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
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20:20:41 [SEVERE] at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
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20:20:41 [SEVERE] at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
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20:20:41 [SEVERE] at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
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20:20:41 [SEVERE] at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
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20:20:41 [SEVERE] at java.security.AccessController.doPrivileged(Native Method)
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20:20:41 [SEVERE] at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
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20:20:41 [SEVERE] at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
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20:20:41 [SEVERE] at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
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20:20:41 [SEVERE] at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
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20:20:41 [SEVERE] at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
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20:20:41 [SEVERE] at java.lang.Class.forName0(Native Method)
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20:20:41 [SEVERE] at java.lang.Class.forName(Class.java:274)
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20:20:41 [SEVERE] at cpw.mods.fml.common.Loader.loadModClass(Loader.java:494)
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20:20:41 [SEVERE] ... 7 more
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20:20:41 [SEVERE] Unexpected exception
cpw.mods.fml.common.LoaderException: cpw.mods.fml.common.LoaderException: java.lang.UnsupportedClassVersionError: net/minecraft/server/mod_NetherOres : Unsupported major.minor version 51.0
at cpw.mods.fml.common.Loader.load(Loader.java:436)
at cpw.mods.fml.common.Loader.loadMods(Loader.java:606)
at cpw.mods.fml.server.FMLBukkitHandler.onPreLoad(FMLBukkitHandler.java:134)
at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:135)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:438)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: cpw.mods.fml.common.LoaderException: java.lang.UnsupportedClassVersionError: net/minecraft/server/mod_NetherOres : Unsupported major.minor version 51.0
at cpw.mods.fml.common.Loader.loadModClass(Loader.java:527)
at cpw.mods.fml.common.Loader.attemptFileLoad(Loader.java:562)
at cpw.mods.fml.common.Loader.load(Loader.java:419)
... 5 more
Caused by: java.lang.UnsupportedClassVersionError: net/minecraft/server/mod_NetherOres : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:274)
at cpw.mods.fml.common.Loader.loadModClass(Loader.java:494)
... 7 more
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I saw one thread recommending to download and install this mod (put it in the mods folder) http://files.minecraftforge.net/LegacyJavaFixer/legacyjavafixer-1.0.jarbut this did not work.

 

It is really bugging me as I cannot find out why it would break.