Win7
Java 1.7(510
MinecraftForge v10.12.0.1019 server
BiomesOPlenty-1.7.2-2.0.0.657

[00:42:36] [Server thread/INFO] [FML]: Forge Mod Loader has identified 4 mods to
load
[00:42:37] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.NoClassDefFoundError: net/minecraft/client/entity/EntityClientPlayerMP

    at biomesoplenty.BiomesOPlenty.<clinit>(BiomesOPlenty.java:47) ~[BiomesO

Plenty.class:?]

Seriously? Giving only a slice of the error log really isn't helpful...

Sorry about that.

[07:19:48] [Server thread/INFO]: Starting minecraft server version 1.7.2
[07:19:51] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.NoClassDefFoundError: net/minecraft/client/entity/EntityClientPlayerMP
at biomesoplenty.BiomesOPlenty.(BiomesOPlenty.java:47) ~[BiomesOPlenty.class:?]
at java.lang.Class.forName0(Native Method) ~[?:1.7.0_51]
at java.lang.Class.forName(Class.java:270) ~[?:1.7.0_51]
at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:443) ~[FMLModContainer.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_51]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_51]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_51]
at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_51]
at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:47) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.EventBus.post(EventBus.java:267) ~[minecraft_server.1.7.2.jar:?]
at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:209) ~[LoadController.class:?]
at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:188) ~[LoadController.class:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.7.0_51]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) ~[?:1.7.0_51]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.7.0_51]
at java.lang.reflect.Method.invoke(Method.java:606) ~[?:1.7.0_51]
at com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:47) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296) ~[minecraft_server.1.7.2.jar:?]
at com.google.common.eventbus.EventBus.post(EventBus.java:267) ~[minecraft_server.1.7.2.jar:?]
at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:119) ~[LoadController.class:?]
at cpw.mods.fml.common.Loader.loadMods(Loader.java:487) ~[Loader.class:?]
at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:76) ~[FMLServerHandler.class:?]
at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:294) ~[FMLCommonHandler.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:114) ~[lj.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:412) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:705) [kx.class:?]
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.entity.EntityClientPlayerMP
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:188) ~[launchwrapper-1.9.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_51]
at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_51]
... 31 more
Caused by: java.lang.NullPointerException
[07:19:51] [Server thread/ERROR]: This crash report has been saved to: E:\vanilla_mc.\crash-reports\crash-2014-01-27_07.19.51-server.txt
[07:19:58] [Server thread/INFO]: Stopping server
[07:19:58] [Server thread/INFO]: Saving worlds

Having the same issue, with any build after 630 (653 to 670).

MC 1.7.2 Server with Forge 1019

Crash-Dump: http://pastebin.com/XCgSKrLQ
Log: http://pastebin.com/1Sy0dCDh