Craftbook error

[INFO] This server is running Craftbukkit version git-Bukkit-0.0.0-493-g8b5496e-b493jnks
[INFO] ChatBukkit v0.0.1 is enabled!
[INFO] CraftBookCommon 3.0-alpha1 enabled.
[INFO] CraftBookCircuits 3.0-alpha1 enabled.
[INFO] CraftBookMechanisms 3.0-alpha1 enabled.
[INFO] CraftBookVehicles 3.0-alpha1 enabled.
[INFO] Rune blacklist with 0 runes loaded.
[INFO] Loaded 2 waypoints, 4 teleporters, 0 position runes, 2 player data sets.
[INFO] Loaded 0 block runes.
[INFO] Runecraft 2.4.4 initialized.
[INFO] Runecraft plugin version 0.1 is enabled!
[INFO] ScrapBukkit version 0.2.1 is enabled!
[INFO] WorldEdit 4.0-beta8 enabled.
[INFO] WorldEdit: No known permissions plugin detected. Using configuration file for permissions.





2011-03-04 14:33:29 [SEVERE] Could not pass event REDSTONE_CHANGE to CraftBookMechanisms
java.lang.NullPointerException
	at org.bukkit.craftbukkit.block.CraftSign.getLine(CraftSign.java:24)
	at com.sk89q.craftbook.mech.Bridge$Factory.detect(Bridge.java:62)
	at com.sk89q.craftbook.mech.Bridge$Factory.detect(Bridge.java:40)
	at com.sk89q.craftbook.MechanicManager.detect(MechanicManager.java:201)
	at com.sk89q.craftbook.MechanicManager.load(MechanicManager.java:171)
	at com.sk89q.craftbook.MechanicManager.dispatchBlockRedstoneChange(MechanicManager.java:135)
	at com.sk89q.craftbook.bukkit.MechanicListenerAdapter$MechanicBlockListener.handleDirectWireInput(MechanicListenerAdapter.java:239)
	at com.sk89q.craftbook.bukkit.MechanicListenerAdapter$MechanicBlockListener.onBlockRedstoneChange(MechanicListenerAdapter.java:181)
	at org.bukkit.plugin.java.JavaPluginLoader$28.execute(JavaPluginLoader.java:262)
	at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:59)
	at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:225)
	at net.minecraft.server.BlockRedstoneWire.a(BlockRedstoneWire.java:110)
	at net.minecraft.server.BlockRedstoneWire.g(BlockRedstoneWire.java:40)
	at net.minecraft.server.BlockRedstoneWire.a(BlockRedstoneWire.java:284)
	at net.minecraft.server.World.k(World.java:369)
	at net.minecraft.server.World.h(World.java:344)
	at net.minecraft.server.World.f(World.java:317)
	at net.minecraft.server.World.b(World.java:302)
	at net.minecraft.server.BlockDiode.a(SourceFile:63)
	at net.minecraft.server.World.a(World.java:1534)
	at net.minecraft.server.World.g(World.java:1433)
	at net.minecraft.server.MinecraftServer.h(MinecraftServer.java:348)
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:272)
	at net.minecraft.server.ThreadServerApplication.run(SourceFile:366)