What steps will reproduce the problem?
Download latex CraftBukkit RB 1.4.5 RB1.0 and start with this plugin

What is the expected output? What do you see instead?
Should be working normally, there is an error

What version of the product are you using?
VanishNoPacket v3.12.4

Do you have an error log of what happened?
13:44:23 [SEVERE] Error occurred while enabling VanishNoPacket v3.12.4 (Is it up to date?)
java.lang.NoClassDefFoundError: net/minecraft/server/Packet
at org.kitteh.vanish.VanishPlugin.onEnable(VanishPlugin.java:279)
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:217)
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:457)
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:381)
at org.bukkit.craftbukkit.v1_4_5.CraftServer.loadPlugin(CraftServer.java:272)
at org.bukkit.craftbukkit.v1_4_5.CraftServer.enablePlugins(CraftServer.java:254)
at net.minecraft.server.v1_4_5.MinecraftServer.j(MinecraftServer.java:320)
at net.minecraft.server.v1_4_5.MinecraftServer.e(MinecraftServer.java:299)
at net.minecraft.server.v1_4_5.MinecraftServer.a(MinecraftServer.java:258)
at net.minecraft.server.v1_4_5.DedicatedServer.init(DedicatedServer.java:147)
at net.minecraft.server.v1_4_5.MinecraftServer.run(MinecraftServer.java:398)
at net.minecraft.server.v1_4_5.ThreadServerApplication.run(SourceFile:856)
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.Packet
at org.bukkit.plugin.java.PluginClassLoader.findClass0(PluginClassLoader.java:70)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:53)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 12 more

Please provide any additional information below.

You're running an outdated version.