For me, Mekanism version 7.1.1.118 causes Minecraft to crash on startup. The Forge version used is 10.13.2.1231. Mekanism version 7.1.1.114 works flawlessly.

Crash report:

---- Minecraft Crash Report ----
// I'm sorry, Dave.

Time: 20.10.14 17:24
Description: Initializing game

java.lang.NoClassDefFoundError: mekanism/common/tile/TileEntityChanceMachine
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at cpw.mods.fml.common.ProxyInjector.inject(ProxyInjector.java:59)
at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:492)
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.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 cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:208)
at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:187)
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.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 cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:118)
at cpw.mods.fml.common.Loader.loadMods(Loader.java:492)
at cpw.mods.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:204)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:480)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:867)
at net.minecraft.client.main.Main.main(SourceFile:148)
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)
Caused by: java.lang.ClassNotFoundException: mekanism.common.tile.TileEntityChanceMachine
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 36 more
Caused by: java.lang.NoClassDefFoundError: mekanism/common/tile/TileEntityBasicMachine
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
... 38 more
Caused by: java.lang.ClassNotFoundException: mekanism.common.tile.TileEntityBasicMachine
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:101)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 42 more

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

-- Head --
Stacktrace:
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at cpw.mods.fml.common.ProxyInjector.inject(ProxyInjector.java:59)
at cpw.mods.fml.common.FMLModContainer.constructMod(FMLModContainer.java:492)
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.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 cpw.mods.fml.common.LoadController.sendEventToModContainer(LoadController.java:208)
at cpw.mods.fml.common.LoadController.propogateStateMessage(LoadController.java:187)
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.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 cpw.mods.fml.common.LoadController.distributeStateMessage(LoadController.java:118)
at cpw.mods.fml.common.Loader.loadMods(Loader.java:492)
at cpw.mods.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:204)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:480)

-- Initialization --
Details:
Stacktrace:
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:867)
at net.minecraft.client.main.Main.main(SourceFile:148)
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)

-- System Details --
Details:
Minecraft Version: 1.7.10
Operating System: Windows 8 (amd64) version 6.2
Java Version: 1.7.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 220644424 bytes (210 MB) / 607649792 bytes (579 MB) up to 2863661056 bytes (2731 MB)
JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx3072m -XX:MaxPermSize=256m
AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.05 FML v7.10.85.1231 Minecraft Forge 10.13.2.1231 21 mods loaded, 21 mods active
mcp{9.05} Minecraft Coder Pack Unloaded->Constructed
FML{7.10.85.1231} Forge Mod Loader Unloaded->Constructed
Forge{10.13.2.1231} Minecraft Forge Unloaded->Constructed
CodeChickenCore{1.0.4.29} CodeChicken Core Unloaded->Constructed
NotEnoughItems{1.0.3.62} Not Enough Items Unloaded->Constructed
bspkrsCore{6.14} bspkrsCore Unloaded->Constructed
ArmorStatusHUD{1.27} ArmorStatusHUD Unloaded->Constructed
StatusEffectHUD{1.26} StatusEffectHUD Unloaded->Constructed
ChickenChunks{1.3.4.13} ChickenChunks Unloaded->Constructed
EnderStorage{1.4.5.24} EnderStorage Unloaded->Constructed
ForgeMultipart{1.1.0.297} Forge Multipart Unloaded->Constructed
Mekanism{7.1.1} Mekanism Unloaded
NEIAddons{1.12.2.9} NEI Addons Unloaded
NEIAddons|Botany{1.12.2.9} NEI Addons: Botany Unloaded
NEIAddons|Forestry{1.12.2.9} NEI Addons: Forestry Unloaded
NEIAddons|CraftingTables{1.12.2.9} NEI Addons: Crafting Tables Unloaded
NEIAddons|ExNihilo{1.12.2.9} NEI Addons: Ex Nihilo Unloaded
NEIPlugins{1.1.0.11-unofficial} NEI Plugins Unofficial Unloaded
Waila{1.5.5} Waila Unloaded
McMultipart{1.1.0.297} Minecraft Multipart Plugin Unloaded
ForgeMicroblock{1.1.0.297} Forge Microblocks Unloaded
Launched Version: 1.7.10-Forge10.13.2.1231
LWJGL: 2.9.1
OpenGL: GeForce GTX 770/PCIe/SSE2 GL version 4.4.0 NVIDIA 344.11, NVIDIA Corporation
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
Anisotropic Filtering: Off (1)

Meh. IC2 API?

I'm crashing aswell, tried builds 114 and 118, they give same crash report starting with
java.lang.NoClassDefFoundError: mekanism/common/item/ItemElectricBow
Forge 10.13.2.1230
Crash log: http://pastebin.com/HgfPWSkH

update: Add to that the recommended old build 92 crashes aswell. This has something to do with new forge compatibility maybe?

Oh, indeed i don't have any IC2 at the moment. I'll try with the experimental.
Works now. Was suggested API download from here: http://ic2api.player.to:8080/job/IC2_experimental/