Minecraft was working normally then kept crashing for no reason (would greatly appreciate help)

[Sure]

An error occurred trying to configure the minecraft home at /Users/(my name)/Library/Application Support/minecraft for Forge Mod Loader java.lang.NoClassDefFoundError: net/minecraftforge/fml/relauncher/IFMLLoadingPlugin at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:760) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:467) at java.net.URLClassLoader.access$100(URLClassLoader.java:73) at java.net.URLClassLoader$1.run(URLClassLoader.java:368) at java.net.URLClassLoader$1.run(URLClassLoader.java:362) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:361) at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:117) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:348) at cpw.mods.fml.relauncher.CoreModManager.loadCoreMod(CoreModManager.java:460) at cpw.mods.fml.relauncher.CoreModManager.discoverCoreMods(CoreModManager.java:389) at cpw.mods.fml.relauncher.CoreModManager.handleLaunch(CoreModManager.java:221) at cpw.mods.fml.relauncher.FMLLaunchHandler.setupHome(FMLLaunchHandler.java:90) at cpw.mods.fml.relauncher.FMLLaunchHandler.setupClient(FMLLaunchHandler.java:67) at cpw.mods.fml.relauncher.FMLLaunchHandler.configureForClientLaunch(FMLLaunchHandler.java:34) at cpw.mods.fml.common.launcher.FMLTweaker.injectIntoClassLoader(FMLTweaker.java:126) at net.minecraft.launchwrapper.Launch.launch(Launch.java:115) at net.minecraft.launchwrapper.Launch.main(Launch.java:28) Caused by: java.lang.ClassNotFoundException: net.minecraftforge.fml.relauncher.IFMLLoadingPlugin at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ... 23 more Caused by: java.lang.NullPointerException at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182) ... 25 more

 

I would greatly appreciate help, this is the only error in the log and Minecraft keeps crashing it only started recently.

[Choonster]

Quote

 

An error occurred trying to configure the minecraft home at /Users/(my name)/Library/Application Support/minecraft for Forge Mod Loader

java.lang.NoClassDefFoundError: net/minecraftforge/fml/relauncher/IFMLLoadingPlugin

 

 

You're running a coremod built for Minecraft 1.8 or later on Minecraft 1.7.10 or earlier, which won't work.

 

Which version of Minecraft are you trying to run? If it's 1.7.10 or earlier, you won't get any help here. If it's 1.8 or later, make sure you're running the right version from the launcher.

[Sure]

Thanks for your reply I was able to find the problem (it was a dummycore mod which didn't specify what version it was.