Server log. This happens with the latest Vault and also causes FalseBook Core and Wireless Redstone to throw NullPointerException errors with VaultPermissions later in the bukkit startup.

[SEVERE] Error occurred while enabling Vault v1.2.16-b184 (Is it up to date?)
java.lang.NoClassDefFoundError: org/bukkit/event/server/ServerListener
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.JavaPluginLoader.getClassByName(JavaPluginLoader.java:234)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:37)
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 net.milkbowl.vault.economy.plugins.Economy_Essentials.(Economy_Essentials.java:55)
at net.milkbowl.vault.Vault.loadEconomy(Vault.java:262)
at net.milkbowl.vault.Vault.onEnable(Vault.java:106)
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:336)
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:381)
at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:256)
at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:238)
at org.bukkit.craftbukkit.CraftServer.(CraftServer.java:190)
at net.minecraft.server.ServerConfigurationManager.(ServerConfigurationManager.java:53)
at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:157)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:423)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Caused by: java.lang.ClassNotFoundException: org.bukkit.event.server.ServerListener
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)
... 28 more

If you can help fix this it will be greatly appreciated! This started happening at a random time, starting before the install of McMMO by a day, but after the install of NoLagg and FalseBook by about a week or two. This error's random occurrance has stumped me for a few days now. In trying to fix this I have updated FalseBook, Essentials, Vault, and Wireless Redstone to no avail.

I use Essentials Permissions.

Make sure you don't have 2 Vault's installed or old plugins, that error will only occur if you have a very outdated plugin from before the 1.1 update and the changes in how plugin listeners works. it is impossible for the latest Vault to get this error as it no longer uses any of the specified classes.

I will go through all the plugins in my free time and make sure they are all updated, thank you for the reply. I will post back with more info when something interesting happens.

There was a rogue Plugins folder lying around, but I found that LWC also caused these errors if it has the wrong configuration even on the right version. Thank you for your help, you were completely right as that plugins folder had an old Vault!