Crashdump: http://pastebin.com/CE85FuHs
Time: 03.05.16 15:58
Description: Updating screen events

java.lang.ClassCastException: net.minecraft.client.entity.EntityPlayerSP cannot be cast to net.minecraft.entity.player.EntityPlayerMP
at mrriegel.furnus.gui.MachineContainer.func_75142_b(MachineContainer.java:99)
at net.minecraft.inventory.Container.func_75144_a(Container.java:470)
at net.minecraft.client.multiplayer.PlayerControllerMP.func_78753_a(PlayerControllerMP.java:488)
at net.minecraft.client.gui.inventory.GuiContainer.func_146984_a(GuiContainer.java:629)
at net.minecraft.client.gui.inventory.GuiContainer.func_146286_b(GuiContainer.java:504)
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:565)
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:524)
at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1674)
at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1024)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:349)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

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

-- Head --
Stacktrace:
at mrriegel.furnus.gui.MachineContainer.func_75142_b(MachineContainer.java:99)
at net.minecraft.inventory.Container.func_75144_a(Container.java:470)
at net.minecraft.client.multiplayer.PlayerControllerMP.func_78753_a(PlayerControllerMP.java:488)
at net.minecraft.client.gui.inventory.GuiContainer.func_146984_a(GuiContainer.java:629)
at net.minecraft.client.gui.inventory.GuiContainer.func_146286_b(GuiContainer.java:504)
at net.minecraft.client.gui.GuiScreen.func_146274_d(GuiScreen.java:565)
at net.minecraft.client.gui.GuiScreen.func_146269_k(GuiScreen.java:524)