Minecraft Crashes after installing Forge

Mods loaded: 1

ModLoader 1.2.5

      Minecraft has crashed!     

      ----------------------     

Minecraft has stopped running because it encountered a problem.

--- BEGIN ERROR REPORT 9f578458 --------

Generated 28/06/12 19:45

Minecraft: Minecraft 1.2.5

OS: Windows 7 (x86) version 6.1

Java: 1.6.0_29, Sun Microsystems Inc.

VM: Java HotSpot Client VM (mixed mode), Sun Microsystems Inc.

LWJGL: 2.4.2

OpenGL: Intel® HD Graphics version 2.1.0 - Build 8.15.10.2622, Intel

cpw.mods.fml.common.LoaderException: java.lang.ClassCastException: mod_MinecraftForge cannot be cast to cpw.mods.fml.common.modloader.BaseMod

at cpw.mods.fml.common.modloader.ModLoaderModContainer.preInit(ModLoaderModContainer.java:114)

at cpw.mods.fml.common.Loader.preModInit(Loader.java:235)

at cpw.mods.fml.common.Loader.loadMods(Loader.java:593)

at cpw.mods.fml.client.FMLClientHandler.onPreLoad(FMLClientHandler.java:193)

at net.minecraft.client.Minecraft.a(Minecraft.java:383)

at net.minecraft.client.Minecraft.run(Minecraft.java:735)

at java.lang.Thread.run(Unknown Source)

Caused by: java.lang.ClassCastException: mod_MinecraftForge cannot be cast to cpw.mods.fml.common.modloader.BaseMod

at cpw.mods.fml.common.modloader.ModLoaderModContainer.preInit(ModLoaderModContainer.java:107)

... 6 more

--- END ERROR REPORT e3f22013 ----------