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java.lang.ClassNotFoundException: mods.MCA.MCA what does that mean and how can i fix it

can somemone help me my mod is crashing ---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 6/15/13 7:46 AM
Description: Failed to start game

cpw.mods.fml.common.LoaderException: java.lang.ClassNotFoundException: mods.MCA.MCA
at cpw.mods.fml.common.LoadController.transition(LoadController.java:142)
at cpw.mods.fml.common.Loader.loadMods(Loader.java:513)
at cpw.mods.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:160)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:410)
at net.minecraft.client.MinecraftAppletImpl.func_71384_a(SourceFile:56)
at net.minecraft.client.Minecraft.run(Minecraft.java:732)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: mods.MCA.MCA
at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at cpw.mods.fml.common.ModClassLoader.loadClass(ModClassLoader.java:56)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:425)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
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:314)
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.propogateStateMessage(LoadController.java:165)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
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:314)
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:98)
at cpw.mods.fml.common.Loader.loadMods(Loader.java:503)
... 5 more
Caused by: java.lang.NullPointerException
at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:227)
... 32 more


A detailed walkthrough of the error, its code path and all known details is as follows:
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-- System Details --
Details:
Minecraft Version: 1.5.2
Operating System: Windows XP (x86) version 5.1
Java Version: 1.7.0_21, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 17973104 bytes (17 MB) / 86585344 bytes (82 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -Xmx1024m -Xmx512m
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 v7.51 FML v5.2.2.684 Minecraft Forge 7.8.0.684 4 mods loaded, 4 mods active
mcp{7.44} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed
FML{5.2.2.684} [Forge Mod Loader] (coremods) Unloaded->Constructed
Forge{7.8.0.684} [Minecraft Forge] (coremods) Unloaded->Constructed
MCA{3.3.5} [Minecraft Comes Alive] (mods) Unloaded->Errored
LWJGL: 2.4.2
OpenGL: Intel Bear Lake B GL version 1.4.0 - Build 7.14.10.4885, Intel
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Texture Pack: SEUS v10 RC7 Ultra.zip
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~~ERROR~~ NullPointerException: null