minecraft crashes when loading

i have installed FML 1.6.4-9.11.1.935 and it works fine with IronChest and CustomNPCs mods, But when i try to use BetterAnvils Mod it crashes while loading.  BetterAnvils says its a problem with the FML class file. please help fix this.

Here is the crash report:

---- Minecraft Crash Report ----

Time: 10/26/13 4:19 PM

Description: There was a severe problem during mod loading that has caused the game to fail

cpw.mods.fml.common.LoaderException: java.lang.ClassNotFoundException: vdvman1.betterAnvil.BetterAnvil

at cpw.mods.fml.common.LoadController.transition(LoadController.java:156)

at cpw.mods.fml.common.Loader.loadMods(Loader.java:519)

at cpw.mods.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:183)

at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:473)

at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:808)

at net.minecraft.client.main.Main.main(SourceFile:101)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at net.minecraft.launchwrapper.Launch.launch(Launch.java:131)

at net.minecraft.launchwrapper.Launch.main(Launch.java:27)

Caused by: java.lang.ClassNotFoundException: vdvman1.betterAnvil.BetterAnvil

at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:186)

at java.lang.ClassLoader.loadClass(ClassLoader.java:306)

at java.lang.ClassLoader.loadClass(ClassLoader.java:247)

at cpw.mods.fml.common.ModClassLoader.loadClass(ModClassLoader.java:61)

at java.lang.Class.forName0(Native Method)

at java.lang.Class.forName(Class.java:249)

at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:462)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)

at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)

at com.google.common.eventbus.EventBus.dispatch(EventBus.java:313)

at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)

at com.google.common.eventbus.EventBus.post(EventBus.java:267)

at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:201)

at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:181)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)

at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)

at com.google.common.eventbus.EventBus.dispatch(EventBus.java:313)

at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)

at com.google.common.eventbus.EventBus.post(EventBus.java:267)

at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:112)

at cpw.mods.fml.common.Loader.loadMods(Loader.java:509)

... 10 more

Caused by: java.lang.NullPointerException

at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:178)

... 38 more

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

---------------------------------------------------------------------------------------

-- System Details --

Details:

Minecraft Version: 1.6.4

Operating System: Mac OS X (x86_64) version 10.8.4

Java Version: 1.6.0_45, Apple Inc.

Java VM Version: Java HotSpot 64-Bit Server VM (mixed mode), Apple Inc.

Memory: 10280600 bytes (9 MB) / 114061312 bytes (108 MB) up to 1065025536 bytes (1015 MB)

JVM Flags: 1 total; -Xmx1G

AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used

Suspicious classes: FML and Forge are installed

IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0

FML: MCP v8.11 FML v6.4.31.935 Minecraft Forge 9.11.1.935 12 mods loaded, 12 mods active

mcp{8.09} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed

FML{6.4.31.935} [Forge Mod Loader] (minecraftforge-9.11.1.935.jar) Unloaded->Constructed

Forge{9.11.1.935} [Minecraft Forge] (minecraftforge-9.11.1.935.jar) Unloaded->Constructed

BetterAnvil{3.0.6} [better Anvils] (BetterAnvils.zip) Unloaded->Errored

customnpcs{0.8} [CustomNpcs] (CustomNPCs_1.zip) Unloaded->Constructed

BuildCraft|Core{4.1.0} [buildCraft] (buildcraft-A-1.6.2-4.1.0.jar) Unloaded->Constructed

BuildCraft|Builders{4.1.0} [bC Builders] (buildcraft-A-1.6.2-4.1.0.jar) Unloaded->Constructed

BuildCraft|Energy{4.1.0} [bC Energy] (buildcraft-A-1.6.2-4.1.0.jar) Unloaded->Constructed

BuildCraft|Factory{4.1.0} [bC Factory] (buildcraft-A-1.6.2-4.1.0.jar) Unloaded->Constructed

BuildCraft|Transport{4.1.0} [bC Transport] (buildcraft-A-1.6.2-4.1.0.jar) Unloaded->Constructed

BuildCraft|Silicon{4.1.0} [bC Silicon] (buildcraft-A-1.6.2-4.1.0.jar) Unloaded->Constructed

IronChest{5.4.1.629} [iron Chest] (ironchest-universal-1-1.zip) Unloaded->Constructed