Namespace...

22:21:21 [SEVERE] Could not load 'plugins\SimplePL.jar' in folder 'plugins': mai
n may not be within the org.bukkit namespace
org.bukkit.plugin.InvalidDescriptionException: main may not be within the org.bu
kkit namespace
        at org.bukkit.plugin.PluginDescriptionFile.loadMap(PluginDescriptionFile
.java:187)
        at org.bukkit.plugin.PluginDescriptionFile.<init>(PluginDescriptionFile.
java:37)
        at org.bukkit.plugin.java.JavaPluginLoader.getPluginDescription(JavaPlug
inLoader.java:188)
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager
.java:119)
        at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:164)
        at org.bukkit.craftbukkit.CraftServer.<init>(CraftServer.java:140)
        at net.minecraft.server.ServerConfigurationManager.<init>(ServerConfigur
ationManager.java:52)
        at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:148)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:408)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)