Minecraft – ClassNotFound exception when attempting to load Minecraft backpack

I am a total novice and posting for my child who downloaded a new mod and seemed to mess up her forge/backpack/mca. I think in trying to fix, I probably messed it up more. Here is the error report:

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

cpw.mods.fml.common.LoaderException: java.lang.ClassNotFoundException: backpack.Backpack
    at cpw.mods.fml.common.ProxyInjector.inject(ProxyInjector.java:75)
    at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:519)
    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:194)
    at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:174)
    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:105)
    at cpw.mods.fml.common.Loader.loadMods(Loader.java:509)
    at cpw.mods.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:181)
    at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:471)
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:806)
    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:57)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:18)
Caused by: java.lang.ClassNotFoundException: backpack.Backpack
    at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:94)
    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:58)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:249)
    at cpw.mods.fml.common.ProxyInjector.inject(ProxyInjector.java:42)
    ... 33 more

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- System Details --
Details:
    Minecraft Version: 1.6.2
    Operating System: Mac OS X (x86_64) version 10.7.5
    Java Version: 1.6.0_65, Apple Inc.
    Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
    Memory: 40509584 bytes (38 MB) / 117997568 bytes (112 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 v8.04 FML v6.2.62.871 Minecraft Forge 9.10.1.871 9 mods loaded, 9 mods active
    mcp{8.04} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed
    FML{6.2.62.871} [Forge Mod Loader] (minecraftforge-9.10.1.871.jar) Unloaded->Constructed
    Forge{9.10.1.871} [Minecraft Forge] (minecraftforge-9.10.1.871.jar) Unloaded->Constructed
    jammyfurniture{4.5} [Jammy Furniture Mod] (1.6.2_Jammy_Furniture_Mod_V4.5) Unloaded->Constructed
    betterbiomes{1.3.0 for MC 1.6.2} [Better Biomes] (Better Biomes 1.3.0 for MC 1.6.2) Unloaded->Constructed
    SKC-BetterWood{1.0.5.0} [Better Wood] (BetterWood 1.0.5.0 - MC 1.6.2 - Forge (9.10.0.789)) Unloaded->Constructed
    Backpack{1.12.15} [Backpack] (MCA v3.5.4-2) Unloaded->Errored
    mca{3.5.4} [Minecraft Comes Alive] (MCA v3.5.4-2) Unloaded->Errored
    mod_ReiMinimap{v3.4_01 [1.6.2]} [mod_ReiMinimap] ([1.6.2]ReiMinimap_v3.4_01) Unloaded->Constructed

Obviously there is something wrong with MCA and backpack, but I have no idea how to fix this without taking everything off and starting over, which will make us lose data? Please help in layman's terms 🙂

Thanks!