I am having same issue, I added Mo' Creatures to my Hexxit server and its keep crashing with this crash report:
---- Minecraft Crash Report ----
// Oops.
Time: 15.4.20 11:23
Description: Exception in server tick loop
java.lang.NoClassDefFoundError: net/minecraft/client/gui/GuiOptions
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
at java.lang.Class.getDeclaredMethods(Unknown Source)
at cpw.mods.fml.common.FMLModContainer.gatherAnnotations(FMLModContainer.java:319)
at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:464)
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 com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)
at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)
at com.google.common.eventbus.EventBus.post(EventBus.java:267)
at cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:192)
at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:172)
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 com.google.common.eventbus.EventHandler.handleEvent(EventHandler.java:74)
at com.google.common.eventbus.SynchronizedEventHandler.handleEvent(SynchronizedEventHandler.java:45)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:314)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:296)
at com.google.common.eventbus.EventBus.post(EventBus.java:267)
at cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:103)
at cpw.mods.fml.common.Loader.loadMods(Loader.java:504)
at cpw.mods.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:85)
at cpw.mods.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:350)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:69)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:431)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.gui.GuiOptions
at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:238)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 32 more
Caused by: java.lang.NullPointerException
at cpw.mods.fml.relauncher.RelaunchClassLoader.findClass(RelaunchClassLoader.java:227)
... 34 more
A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------
-- System Details --
Details:
Minecraft Version: 1.5.2
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_241, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 261500608 bytes (249 MB) / 374341632 bytes (357 MB) up to 1890582528 bytes (1803 MB)
JVM Flags: 0 total;
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Suspicious classes: FML and Forge are installed
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v7.51 FML v5.2.23.737 Minecraft Forge 7.8.1.737 59 mods loaded, 59 mods active
mcp{7.51} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed
FML{5.2.23.737} [Forge Mod Loader] (coremods) Unloaded->Constructed
Forge{7.8.1.737} [Minecraft Forge] (coremods) Unloaded->Constructed
CodeChickenCore{0.8.7.3} [CodeChicken Core] (coremods) Unloaded->Constructed
CoFHFramework{1.5.2.5} [CoFH Framework] (coremods) Unloaded->Constructed
ImmibisMicroblocks{55.0.7} [Immibis's Microblocks] (coremods) Unloaded->Constructed
NotEnoughItems{1.5.2.28} [Not Enough Items] (coremods) Unloaded->Constructed
mod_bspkrsCore{v2.09(1.5.2)} [bspkrsCore] ([1.5.2]bspkrsCorev2.09.zip) Unloaded->Constructed
TreeCapitator{Forge 1.5.2.r14} [TreeCapitator] ([1.5.2]TreeCapitator.Forge.1.5.2.r14.Uni.CoreMod.jar) Unloaded->Constructed
CoFHCore{1.5.2.5} [CoFHCore] (CoFHCore-1.5.2.5.jar) Unloaded->Constructed
CoFHWorld{1.5.2.5} [CoFHWorld] (CoFHCore-1.5.2.5.jar) Unloaded->Constructed
GuiAPI{0.15.6} [GuiAPI] (GuiAPI-0.15.6-1.5.2.jar) Unloaded
ImmibisMicroblocksInstallCheck{55.0.7} [Immibis's Microblocks (Checks for incorrect installation, ignore this)] (immibis-microblocks-55.0.7.jar) Unloaded
DamageIndicatorsMod{2.7.0.1} [Damage Indicators] (1.5.2 DamageIndicators v2.7.0.1.zip) Unloaded
AsgardShield_Core{2.0.4} [AsgardShield] (1.5.2AsgardShield_Core_2.0.4Forge.zip) Unloaded
ASAddon_Hallowed{2.0.0} [AS Addon- Hallowed] (1.5.2ASAddonHallowed_v2.0.0Forge.zip) Unloaded
HarkenScythe_Core{2.1.6} [HarkenScythe] (1.5.2HarkenScythe_v2.1.6Forge.zip) Unloaded
ASAddon_HarkenScythe{2.0.0} [AS Addon- HarkenScythe] (1.5.2ASAddonHarkenScythe_v2.0.0Forge.zip) Unloaded
ASAddon_NetherEnder{2.0.0} [AS Addon- Nether-Ender] (1.5.2ASAddonNetherEnder_v2.0.0Forge.zip) Unloaded
ASAddon_ColorAPI{1.0.0} [ASAddon_ColorAPI] (1.5.2AsgardShield_Core_2.0.4Forge.zip) Unloaded
BetterStorage{0.6.2.23-hotfix2} [BetterStorage] ([1.5.2]BetterStorage_0.6.2.23-hotfix2.zip) Unloaded
Artifice{1.5.2R1.1.2} [Artifice] (Artifice-1.1.2-182.jar) Unloaded
ArtificeCompat|Chisel{1.5.2R1.1.2} [Artifice Compat: Chisel] (Artifice-1.1.2-182.jar) Unloaded
ArtificeCompat|EE3{1.5.2R1.1.2} [Artifice Compat: EE3] (Artifice-1.1.2-182.jar) Unloaded
ArtificeCompat|Forestry{1.5.2R1.1.2} [Artifice Compat: Forestry] (Artifice-1.1.2-182.jar) Unloaded
ArtificeCompat|MFR{1.5.2R1.1.2} [Artifice Compat: MFR] (Artifice-1.1.2-182.jar) Unloaded
ArtificeCompat|Railcraft{1.5.2R1.1.2} [Artifice Compat: Railcraft] (Artifice-1.1.2-182.jar) Unloaded
ArtificeCompat|Vanilla{1.5.2R1.1.2} [Artifice Compat: Vanilla] (Artifice-1.1.2-182.jar) Unloaded
Backpack{1.12.13} [Backpack] (backpack-1.12.13-1.5.2.zip) Unloaded
BattleTowers{1.3.4} [Battle Towers] (BattleTowers_1.5.2.zip) Unloaded
BetterDungeons{1.8} [Better dungeons] (BetterDungeons.zip) Unloaded
BiblioCraft{1.3.3} [BiblioCraft] (BiblioCraft[v1.3.3].zip) Unloaded
ChestTransporter{1.1.6} [Chest Transporter] (chestTransporter_1.1.6_Universal.zip) Unloaded
CustomSpawner{2.2.2} [DrZhark's CustomSpawner] (CustomMobSpawner 2.2.2.zip) Unloaded
DimDoors{1.5.2R1.4.1RC1} [Dimensional Doors] (DimensionalDoors-1.5.2R1.4.1RC1-194.zip) Unloaded
MoCreatures{5.2.3} [DrZhark's Mo'Creatures Mod] (DrZharks MoCreatures Mod v5.2.3.zip) Unloaded
eplus{1.15.4} [Enchanting Plus] (EnchantingPlus-1.15.4.jar) Unloaded
ExtrabiomesXL{3.13.4} [ExtrabiomesXL] (ExtrabiomesXL-universal-1.5.2-3.13.4.jar) Unloaded
hexxitgear{1.5.2R1.0} [Hexxit Gear] (HexxitGear-1.0-23.jar) Unloaded
ImmibisCore{55.1.6} [Immibis Core] (immibis-core-55.1.6.jar) Unloaded
InfernalMobs{1.3.1} [Infernal Mobs] (InfernalMobs_1.5.2.zip) Unloaded
Meteors{2.10.2} [Falling Meteors] (Meteors Mod V2.10.2.zip) Unloaded
More Bows{1.5_v1} [More Bows mod] (More bows 1.5.2_2 Forge.jar) Unloaded
Natura{2.1.5} [Natura] (Natura_1.5.2_2.1.5.1.jar) Unloaded
Natura|CompatMineFactoryReloaded{0.1} [Natura compat: MFR] (Natura_1.5.2_2.1.5.1.jar) Unloaded
LegendGear{1.5.2} [LegendGear] (NMcCoy-LegendGear-1.5.2.zip) Unloaded
ObsidiPlates{1.5.0} [Obsidian Pressure Plates] (obsidiplates-1.5.2-universal-1.5.0.13.jar) Unloaded
OffLawn{1.0} [offLawn] (OffLawn-1.5.1.zip) Unloaded
QuantumCraft{1.01} [qCraft] (qCraft1.01.zip) Unloaded
xreliquary{1.5.2} [Xeno's Reliquary] (Reliquary1.0.6d.zip) Unloaded
rftl{1.0} [RottenFleshToLeather] (RottenFleshToLeather-1.5.1.zip) Unloaded
AS_Ruins{10.3} [Ruins Spawning System] (Ruins_1.5.2.zip) Unloaded
secretroomsmod{4.6.0} [SecretRoomsMod] (SecretRoomsMod-universal-4.6.0.283.zip) Unloaded
SoulShards{1.0.16} [Soul Shards] (SoulShards-1.0.36-universal-srg.jar) Unloaded
TConstruct{1.5.2_1.4.3d7} [Tinkers' Construct] (TConstruct_1.5.2_1.4.3.final.jar) Unloaded
TConstruct|CompatMineFactoryReloaded{0.1} [TConstruct Compat: MFR] (TConstruct_1.5.2_1.4.3.final.jar) Unloaded
TwilightForest{1.18.1} [The Twilight Forest] (twilightforest-1.18.1.zip) Unloaded
WildCaves3{0.4.2} [Wild Caves 3] (WildCaves3-0.4.2.zip) Unloaded
chococraft{2.8.8} [Torojima's ChocoCraft] (zzzChococraft_2.8.8.zip) Unloaded
Profiler Position: N/A (disabled)
Is Modded: Definitely; Server brand changed to 'fml,forge'
Type: Dedicated Server (map_server.txt)
Please help me fix this.