dw20 error

2013-12-19 00:03:27 [SEVERE] Encountered an unexpected exception NoClassDefFoundError
java.lang.NoClassDefFoundError: net/minecraft/inventory/ContainerWorkbench
	at net.minecraft.server.management.ServerConfigurationManager.func_72366_a(ServerConfigurationManager.java:389)
	at net.minecraft.network.NetLoginHandler.completeConnection(NetLoginHandler.java:197)
	at cpw.mods.fml.common.network.FMLNetworkHandler.handleClientConnection(FMLNetworkHandler.java:167)
	at cpw.mods.fml.common.network.FMLNetworkHandler.onConnectionReceivedFromClient(FMLNetworkHandler.java:121)
	at net.minecraft.network.NetLoginHandler.func_72529_d(NetLoginHandler.java:185)
	at net.minecraft.network.NetLoginHandler.func_72532_c(NetLoginHandler.java:71)
	at net.minecraft.server.ServerListenThread.func_71766_a(ServerListenThread.java:55)
	at net.minecraft.server.dedicated.DedicatedServerListenThread.func_71747_b(SourceFile:29)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:691)
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:276)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
	at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)
Caused by: java.lang.ClassNotFoundException: net.minecraft.inventory.ContainerWorkbench
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:186)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	... 13 more
Caused by: java.lang.OutOfMemoryError: PermGen space
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(Unknown Source)
	at java.security.SecureClassLoader.defineClass(Unknown Source)
	at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:178)
	... 15 more
2013-12-19 00:03:29 [INFO] Stopping server