Ok here is the report file!

---- Minecraft Crash Report ----
// You're mean.

Time: 2013-09-01 14:35
Description: Rendering screen

java.lang.NoClassDefFoundError: micdoodle8/mods/galacticraft/core/entities/GCCorePlayerMP
at net.minecraft.server.integrated.IntegratedServer.<init>(IntegratedServer.java:54)
at net.minecraft.client.Minecraft.func_71371_a(Minecraft.java:1987)
at net.minecraft.client.gui.GuiSelectWorld.func_74064_e(SourceFile:157)
at net.minecraft.client.gui.GuiWorldSlot.func_77213_a(SourceFile:210)
at net.minecraft.client.gui.GuiSlot.func_77211_a(GuiSlot.java:247)
at net.minecraft.client.gui.GuiSelectWorld.func_73863_a(SourceFile:183)
at net.minecraft.client.renderer.EntityRenderer.func_78480_b(EntityRenderer.java:1036)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:934)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:826)
at net.minecraft.client.main.Main.main(SourceFile:101)
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 net.minecraft.launchwrapper.Launch.launch(Launch.java:57)
at net.minecraft.launchwrapper.Launch.main(Launch.java:18)
Caused by: java.lang.ClassNotFoundException: micdoodle8.mods.galacticraft.core.entities.GCCorePlayerMP
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:179)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 16 more
Caused by: java.lang.NullPointerException
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:171)
... 18 more


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

-- Head --
Stacktrace:
at net.minecraft.server.integrated.IntegratedServer.<init>(IntegratedServer.java:54)
at net.minecraft.client.Minecraft.func_71371_a(Minecraft.java:1987)
at net.minecraft.client.gui.GuiSelectWorld.func_74064_e(SourceFile:157)
at net.minecraft.client.gui.GuiWorldSlot.func_77213_a(SourceFile:210)
at net.minecraft.client.gui.GuiSlot.func_77211_a(GuiSlot.java:247)
at net.minecraft.client.gui.GuiSelectWorld.func_73863_a(SourceFile:183)

-- Screen render details --
Details:
Screen name: net.minecraft.client.gui.GuiMainMenu
Mouse location: Scaled: (212, 113). Absolute: (424, 253)
Screen size: Scaled: (427, 240). Absolute: (854, 480). Scale factor of 2
Stacktrace:
at net.minecraft.client.renderer.EntityRenderer.func_78480_b(EntityRenderer.java:1036)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:934)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:826)
at net.minecraft.client.main.Main.main(SourceFile:101)
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 net.minecraft.launchwrapper.Launch.launch(Launch.java:57)
at net.minecraft.launchwrapper.Launch.main(Launch.java:18)

-- System Details --
Details:
Minecraft Version: 1.6.2
Operating System: Windows 8 (x86) version 6.2
Java Version: 1.7.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 75794448 bytes (72 MB) / 157696000 bytes (150 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -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 v8.04 FML v6.2.55.842 Minecraft Forge 9.10.0.842 5 mods loaded, 5 mods active
mcp{8.04} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
FML{6.2.55.842} [Forge Mod Loader] (coremods) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Forge{9.10.0.842} [Minecraft Forge] (coremods) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Micdoodlecore{} [Micdoodle8 Core] (coremods) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
TC{4.1.0_006} [Traincraft] (traincraft-4.1.0_006.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available
Launched Version: 1.6.2-Forge9.10.0.842
LWJGL: 2.9.0
OpenGL: AMD Radeon HD 7500G + 7500M/7600M Dual Graphics GL version 4.2.11774 Compatibility Profile Context, ATI Technologies Inc.
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Pack: Default
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: ~~ERROR~~ NullPointerException: null