Having a problem with biomes o plenty crashing on launch, I am using the latest curse download version of biomes o plenty for 1.9 (BiomesOPlenty-1.9-4.0.2.2018-universal.jar) and my forge is the latest version for 1.9 (Minecraft 1.9-forge1.9-12.16.0.1809-1.9) The crash happens with optifine installed and also without it installed, and no other mods are involved.

Crash report for without optifine -

---- Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 22/05/16 18:37
Description: There was a severe problem during mod loading that has caused the game to fail

net.minecraftforge.fml.common.LoaderException: java.lang.NoClassDefFoundError: net/minecraftforge/fml/common/registry/IForgeRegistryEntry
at net.minecraftforge.fml.common.LoadController.transition(LoadController.java:172)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:559)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:240)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:434)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:346)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.NoClassDefFoundError: net/minecraftforge/fml/common/registry/IForgeRegistryEntry
at biomesoplenty.core.BiomesOPlenty.preInit(BiomesOPlenty.java:69)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:560)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:221)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:199)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:128)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:556)
... 10 more
Caused by: java.lang.ClassNotFoundException: net.minecraftforge.fml.common.registry.IForgeRegistryEntry
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)
... 38 more
Caused by: java.lang.NullPointerException
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
... 40 more

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

-- System Details --
Details:
Minecraft Version: 1.9
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 77733960 bytes (74 MB) / 285233152 bytes (272 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.23 Powered by Forge 12.16.0.1809 4 mods loaded, 4 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCH mcp{9.19} Minecraft Coder Pack
UCH FML{8.0.99.99} Forge Mod Loader
UCH Forge{12.16.0.1809} Minecraft Forge
UCE BiomesOPlenty{4.0.2.2018} Biomes O' Plenty
Loaded coremods (and transformers):
GL info: ' Vendor: 'NVIDIA Corporation' Version: '4.5.0 NVIDIA 355.60' Renderer: 'GeForce GTX 750 Ti/PCIe/SSE2'

Hopefully someone can help!

Update your Forge, you're using an ancient version.