Cannot install the Forge 6.4.x

[OUGHT]

Hello! I have a problem with 6.4.x versions of Forge.

When I try to install it to the SMP (either extracting into minecraft_server.jar or running minecraftforge.jar) I recieve error:

 

Exception in thread "main" java.lang.IncompatibleClassChangeError: Implementing

class

        at java.lang.ClassLoader.defineClass1(Native Method)

        at java.lang.ClassLoader.defineClass(Unknown Source)

        at java.security.SecureClassLoader.defineClass(Unknown Source)

        at java.net.URLClassLoader.defineClass(Unknown Source)

        at java.net.URLClassLoader.access$100(Unknown Source)

        at java.net.URLClassLoader$1.run(Unknown Source)

        at java.net.URLClassLoader$1.run(Unknown Source)

        at java.security.AccessController.doPrivileged(Native Method)

        at java.net.URLClassLoader.findClass(Unknown Source)

        at java.lang.ClassLoader.loadClass(Unknown Source)

        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)

        at java.lang.ClassLoader.loadClass(Unknown Source)

        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

 

Tried multiple versions of Forge, looked through forum, did not found the solve. Please, help me.

[SanAndreaP]

What version of your server do you have?

 

Also did you delete the files with MOJANG in their filename inside the META-INF folder after installing Forge?

[luacs1998]

Ensure that you are running server for 1.4.5.