Galacticraft NASA Workbench breaking

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 30/03/13 15:07
Description: Exception in server tick loop

java.lang.NoClassDefFoundError: net/minecraft/client/gui/GuiScreen
	at micdoodle8.mods.galacticraft.core.tile.GCCoreTileEntityAdvancedCraftingTable.onDestroy(GCCoreTileEntityAdvancedCraftingTable.java:90)
	at universalelectricity.prefab.multiblock.TileEntityMulti.onBlockRemoval(TileEntityMulti.java:59)
	at universalelectricity.prefab.multiblock.BlockMulti.func_71852_a(BlockMulti.java:60)
	at net.minecraft.world.chunk.Chunk.func_76592_a(Chunk.java:720)
	at net.minecraft.world.World.func_72832_d(World.java:553)
	at micdoodle8.mods.galacticraft.core.tile.GCCoreTileEntityAdvancedCraftingTable.onDestroy(GCCoreTileEntityAdvancedCraftingTable.java:91)
	at universalelectricity.prefab.multiblock.TileEntityMulti.onBlockRemoval(TileEntityMulti.java:59)
	at universalelectricity.prefab.multiblock.BlockMulti.func_71852_a(BlockMulti.java:60)
	at net.minecraft.world.chunk.Chunk.func_76592_a(Chunk.java:720)
	at net.minecraft.world.World.func_72832_d(World.java:553)
	at micdoodle8.mods.galacticraft.core.tile.GCCoreTileEntityAdvancedCraftingTable.onDestroy(GCCoreTileEntityAdvancedCraftingTable.java:91)
	at universalelectricity.prefab.multiblock.TileEntityMulti.onBlockRemoval(TileEntityMulti.java:59)
	at universalelectricity.prefab.multiblock.BlockMulti.func_71852_a(BlockMulti.java:60)
	at net.minecraft.world.chunk.Chunk.func_76592_a(Chunk.java:720)
	at net.minecraft.world.World.func_72832_d(World.java:553)
	at micdoodle8.mods.galacticraft.core.tile.GCCoreTileEntityAdvancedCraftingTable.onDestroy(GCCoreTileEntityAdvancedCraftingTable.java:91)
	at micdoodle8.mods.galacticraft.core.blocks.GCCoreBlockAdvancedCraftingTable.func_71852_a(GCCoreBlockAdvancedCraftingTable.java:147)
	at net.minecraft.world.chunk.Chunk.func_76592_a(Chunk.java:720)
	at net.minecraft.world.World.func_72832_d(World.java:553)
	at net.minecraft.world.World.func_94571_i(World.java:682)
	at net.minecraft.block.Block.removeBlockByPlayer(Block.java:1625)
	at net.minecraft.item.ItemInWorldManager.func_73079_d(ItemInWorldManager.java:275)
	at net.minecraft.item.ItemInWorldManager.func_73084_b(ItemInWorldManager.java:331)
	at net.minecraft.item.ItemInWorldManager.func_73082_a(ItemInWorldManager.java:238)
	at net.minecraft.network.NetServerHandler.func_72510_a(NetServerHandler.java:500)
	at net.minecraft.network.packet.Packet14BlockDig.func_73279_a(SourceFile:46)
	at net.minecraft.network.TcpConnection.func_74428_b(TcpConnection.java:461)
	at net.minecraft.network.NetServerHandler.func_72570_d(NetServerHandler.java:134)
	at net.minecraft.network.NetworkListenThread.func_71747_b(NetworkListenThread.java:53)
	at net.minecraft.server.dedicated.DedicatedServerListenThread.func_71747_b(SourceFile:30)
	at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:674)
	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:274)
	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:570)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:468)
	at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.gui.GuiScreen
	at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:211)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	at java.lang.ClassLoader.loadClass(Unknown Source)
	... 35 more
Caused by: java.lang.NullPointerException
	at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:200)
	... 37 more


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
	Minecraft Version: 1.5.1
	Operating System: Windows XP (x86) version 5.1
	Java Version: 1.7.0_17, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
	Memory: 65722640 bytes (62 MB) / 144224256 bytes (137 MB) up to 1067057152 bytes (1017 MB)
	JVM Flags: 2 total; -Xincgc -Xmx1024M
	AABB Pool Size: 1204 (67424 bytes; 0 MB) allocated, 838 (46928 bytes; 0 MB) used
	Suspicious classes: FML and Forge are installed
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	FML: MCP v7.44 FML v5.1.8.608 Minecraft Forge 7.7.0.608 4 mods loaded, 4 mods active
	mcp [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	FML [Forge Mod Loader] (coremods) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	Forge [Minecraft Forge] (coremods) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	GalacticraftCore [Galacticraft Core] (Galacticraft-Alpha-0.1.29.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 1899 (106344 bytes; 0 MB) allocated, 1529 (85624 bytes; 0 MB) used
	Player Count: 1 / 4; [GCCorePlayerMP['MrXANA91'/67, l='world', x=-54,29, y=72,00, z=-255,17]]
	Is Modded: Definitely; Server brand changed to 'fml'
	Type: Dedicated Server (map_server.txt)