Bukkit

This server is running CraftBukkit version git-Spigot-844 (MC: 1.5.2) (Implementing API version 1.5.2-R0.2-SNAPSHOT)

2013-05-04 09:06:35 [INFO] Melonking issued server command: /season weather sun
2013-05-04 09:06:35 [SEVERE] null
org.bukkit.command.CommandException: Unhandled exception executing command 'season' in plugin Seasons v2.0.3beta
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46)
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
    at org.bukkit.craftbukkit.v1_5_R3.CraftServer.dispatchCommand(CraftServer.java:547)
    at net.minecraft.server.v1_5_R3.PlayerConnection.handleCommand(PlayerConnection.java:979)
    at net.minecraft.server.v1_5_R3.PlayerConnection.chat(PlayerConnection.java:895)
    at net.minecraft.server.v1_5_R3.PlayerConnection.a(PlayerConnection.java:840)
    at net.minecraft.server.v1_5_R3.Packet3Chat.handle(Packet3Chat.java:44)
    at org.spigotmc.netty.NettyNetworkManager.b(NettyNetworkManager.java:186)
    at net.minecraft.server.v1_5_R3.PlayerConnection.d(PlayerConnection.java:109)
    at net.minecraft.server.v1_5_R3.ServerConnection.b(SourceFile:35)
    at org.spigotmc.MultiplexingServerConnection.b(MultiplexingServerConnection.java:72)
    at net.minecraft.server.v1_5_R3.MinecraftServer.r(MinecraftServer.java:583)
    at net.minecraft.server.v1_5_R3.DedicatedServer.r(DedicatedServer.java:224)
    at net.minecraft.server.v1_5_R3.MinecraftServer.q(MinecraftServer.java:472)
    at net.minecraft.server.v1_5_R3.MinecraftServer.run(MinecraftServer.java:404)
    at net.minecraft.server.v1_5_R3.ThreadServerApplication.run(SourceFile:573)
Caused by: java.lang.NoClassDefFoundError: net/minecraft/server/v1_5_R2/World
    at org.rominos2.Seasons.Managers.SnowManager.SeasonsSnowManager.start(SeasonsSnowManager.java:67)
    at org.rominos2.Seasons.Managers.SnowManager.SeasonsSnowManager.onWeatherChange(SeasonsSnowManager.java:58)
    at org.rominos2.Seasons.Managers.SeasonsManager.changeWeather(SeasonsManager.java:174)
    at org.rominos2.Seasons.SeasonsCommands.weather(SeasonsCommands.java:150)
    at org.rominos2.Seasons.SeasonsCommands.playerCommand(SeasonsCommands.java:36)
    at org.rominos2.Seasons.Seasons.onCommand(Seasons.java:105)
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44)
    ... 15 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_5_R2.World
    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(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 22 more

Is fixed with 2.0.3