package mod.flatcoloredblocks.gui;

import net.minecraft.client.gui.GuiScreen;
import net.minecraftforge.fml.client.FMLConfigGuiFactory;

/**
 * Basic Config Factory.
 */
public class ConfigGuiFactory extends FMLConfigGuiFactory
{

	@Override
	public Class<? extends GuiScreen> mainConfigGuiClass()
	{
		return ConfigGui.class;
	}

}

@@ -248,24 +248,8 @@
 lic 
-Class%3C? extends 
 GuiS
@@ -257,14 +257,15 @@
 reen
-%3E main
+ create
 Conf
@@ -273,14 +273,36 @@
 gGui
-Class(
+(%0A%09%09%09GuiScreen parentScreen 
 )%0A%09%7B
@@ -311,16 +311,20 @@
 %09return 
+new 
 ConfigGu
@@ -328,14 +328,24 @@
 gGui
-.class
+( parentScreen )
 ;%0A%09%7D

Use createConfigGui instead of mainConfigGuiClass