SignShop console error log

[11:53:39 ERROR]: Could not pass event SSLinkEvent to SignShop v2.9.1Dev
org.bukkit.event.EventException
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:302) ~[spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) ~[spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:509) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:494) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.wargamer2010.signshop.SignShop.scheduleEvent(SignShop.java:205) [SignShop.jar:?]
        at org.wargamer2010.signshop.util.signshopUtil.registerClickedMaterial(signshopUtil.java:451) [SignShop.jar:?]
        at org.wargamer2010.signshop.util.signshopUtil.registerClickedMaterial(signshopUtil.java:438) [SignShop.jar:?]
        at org.wargamer2010.signshop.util.signshopUtil.registerClickedMaterial(signshopUtil.java:433) [SignShop.jar:?]
        at org.wargamer2010.signshop.listeners.SignShopPlayerListener.onPlayerInteract(SignShopPlayerListener.java:163) [SignShop.jar:?]
        at sun.reflect.GeneratedMethodAccessor101.invoke(Unknown Source) ~[?:?]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_72]
        at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_72]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:298) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:509) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:494) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at org.bukkit.craftbukkit.v1_7_R4.event.CraftEventFactory.callPlayerInteractEvent(CraftEventFactory.java:242) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.PlayerInteractManager.dig(PlayerInteractManager.java:103) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.PlayerConnection.a(PlayerConnection.java:552) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.PacketPlayInBlockDig.a(PacketPlayInBlockDig.java:41) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.PacketPlayInBlockDig.handle(PacketPlayInBlockDig.java:65) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.NetworkManager.a(NetworkManager.java:186) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.ServerConnection.c(ServerConnection.java:81) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:734) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:289) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:584) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java:490) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:628) [spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
Caused by: java.lang.NoSuchMethodError: me.ryanhamshire.GriefPrevention.GriefPrevention.allowBuild(Lorg/bukkit/entity/Player;Lorg/bukkit/Location;)Ljava/lang/String;
        at org.wargamer2010.signshop.hooks.GriefPreventionHook.canBuild(GriefPreventionHook.java:20) ~[?:?]
        at org.wargamer2010.signshop.hooks.HookManager.canBuild(HookManager.java:51) ~[?:?]
        at org.wargamer2010.signshop.listeners.sslisteners.SimpleBlockProtector.onSSLinkEvent(SimpleBlockProtector.java:17) ~[?:?]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_72]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_72]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_72]
        at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_72]
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:298) ~[spigot.jar:git-Spigot-1.7.9-R0.2-207-g03373bb]
        ... 27 more