Unsupported major.minor version 51.0

I know there have been a lot of threads about this (ive been searching for answers to my problem) but the threads i have seen are from developers and this got something to do with compiling. Now i'm not a plugin developer and i get this error for Mini-SkyBlock and MCPCPlusXNmsBlock_147, how can i fix this? Using latest recommended Bukkit build.

Errors:

MCPCPlusXNmsBlock_147 (I have no idea what this is, can anyone explain?)

Code:

2013-02-08 17:16:55 [SEVERE] java.lang.UnsupportedClassVersionError: MCPCPlusXNmsBlock_147 : Unsupported major.minor version 51.0
2013-02-08 17:16:55 [SEVERE]    at java.lang.ClassLoader.defineClass1(Native Method)
2013-02-08 17:16:55 [SEVERE]    at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
2013-02-08 17:16:55 [SEVERE]    at java.lang.ClassLoader.defineClass(ClassLoader.java:480)
2013-02-08 17:16:55 [SEVERE]    at com.sk89q.worldedit.bukkit.BukkitWorld$NmsBlockClassLoader.loadClass(BukkitWorld.java:228)
2013-02-08 17:16:55 [SEVERE]    at com.sk89q.worldedit.bukkit.BukkitWorld.<init>(BukkitWorld.java:146)
2013-02-08 17:16:55 [SEVERE]    at com.sk89q.worldedit.bukkit.BukkitUtil.getLocalWorld(BukkitUtil.java:50)
2013-02-08 17:16:55 [SEVERE]    at com.sk89q.worldedit.bukkit.BukkitPlayer.getWorld(BukkitPlayer.java:132)
2013-02-08 17:16:55 [SEVERE]    at com.sk89q.worldedit.bukkit.WorldEditListener.onPlayerInteract(WorldEditListener.java:121)
2013-02-08 17:16:55 [SEVERE]    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2013-02-08 17:16:55 [SEVERE]    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
2013-02-08 17:16:55 [SEVERE]    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
2013-02-08 17:16:55 [SEVERE]    at java.lang.reflect.Method.invoke(Method.java:616)
2013-02-08 17:16:55 [SEVERE]    at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:425)
2013-02-08 17:16:55 [SEVERE]    at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
2013-02-08 17:16:55 [SEVERE]    at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:477)
2013-02-08 17:16:55 [SEVERE]    at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:462)
2013-02-08 17:16:55 [SEVERE]    at org.bukkit.craftbukkit.v1_4_R1.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:178)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.PlayerInteractManager.dig(PlayerInteractManager.java:114)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.PlayerConnection.a(PlayerConnection.java:564)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.Packet14BlockDig.handle(SourceFile:46)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.NetworkManager.b(NetworkManager.java:290)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.PlayerConnection.d(PlayerConnection.java:113)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.ServerConnection.b(SourceFile:39)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.DedicatedServerConnection.b(SourceFile:30)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.MinecraftServer.r(MinecraftServer.java:598)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.DedicatedServer.r(DedicatedServer.java:224)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.MinecraftServer.q(MinecraftServer.java:494)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:427)
2013-02-08 17:16:55 [SEVERE]    at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)

and Mini-Skyblock

Code:

2013-02-08 17:16:04 [SEVERE] Could not load 'plugins/Mini-SkyBlock_v0.2.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.UnsupportedClassVersionError: me/minecraftreagan/sb/skySMP : Unsupported major.minor version 51.0
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:184)
    at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:305)
    at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:230)
    at org.bukkit.craftbukkit.v1_4_R1.CraftServer.loadPlugins(CraftServer.java:239)
    at org.bukkit.craftbukkit.v1_4_R1.CraftServer.<init>(CraftServer.java:217)
    at net.minecraft.server.v1_4_R1.PlayerList.<init>(PlayerList.java:55)
    at net.minecraft.server.v1_4_R1.DedicatedPlayerList.<init>(SourceFile:11)
    at net.minecraft.server.v1_4_R1.DedicatedServer.init(DedicatedServer.java:104)
    at net.minecraft.server.v1_4_R1.MinecraftServer.run(MinecraftServer.java:399)
    at net.minecraft.server.v1_4_R1.ThreadServerApplication.run(SourceFile:849)
Caused by: java.lang.UnsupportedClassVersionError: me/minecraftreagan/sb/skySMP : Unsupported major.minor version 51.0
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
    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 org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:80)
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:264)
    at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:173)
    ... 9 more

 

both plugins require java 7. you only have java 6.

 

Weird... Cuz:

java version "1.7.0_05"
Java(TM) SE Runtime Environment (build 1.7.0_05-b06)
Java HotSpot(TM) 64-Bit Server VM (build 23.1-b03, mixed mode)

Or am i supposed to update some kind of library the minecraft server is using?

 

can you paste your start.bat?

 

I'm running the server on a dedicated server so using PuTTY console to start the server and i use this command line:

java -Xmn2048M -Xincgc -Xmx1024M -jar craftbukkit.jar nogui

 

When you run the command: "java -version" once you SSH in, what's the output?

 

java version "1.7.0_05"
Java(TM) SE Runtime Environment (build 1.7.0_05-b06)
Java HotSpot(TM) 64-Bit Server VM (build 23.1-b03, mixed mode)

Should be good, no?

 

try downloading and installing Java7u10.

 

Should be good. Try doing as orange451 said (although I doubt that will make a difference) and if that still doesn't work, contact the makers of those plugins.

 

It will make a difference, I've dealt with my fair share of these "Unsupported major.minor version 51.0" errors