WorldGuard plugin error help!

I keep seeing this error in my server console, and it's causing semi-massive lag. Anyone know how to fix this?

2012-04-02 15:38:33 [SEVERE] Could not pass event PlayerMoveEvent to WorldGuard
org.bukkit.event.EventException
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:303)
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:62)
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:459)
at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:209)
at net.minecraft.server.Packet10Flying.handle(SourceFile:126)
at net.minecraft.server.NetworkManager.b(NetworkManager.java:229)
at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:113)
at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:554)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:452)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:490)
Caused by: java.lang.NoSuchMethodError: org.bukkit.entity.Player.getVehicle()Lorg/bukkit/entity/Vehicle;
at com.sk89q.worldguard.bukkit.WorldGuardPlayerListener$PlayerMoveHandler.onPlayerMove(WorldGuardPlayerListener.java:113)
at sun.reflect.GeneratedMethodAccessor188.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:301)