I'm having the same error with both ic2 1.60 and ic2 1.71 It seems to be a problem with ic2 but not sure how....
Mods loaded: 25
ModLoader 1.1
mod_ModLoaderMp 1.0.0
mod_Planes 1.1v16
mod_IDResolver 1.1 - Update 0
mod_TooManyItems 1.1 2012-01-12a
mod_ThaumCraft 1.2
mod_StuffedAnimals 1.8.1
mod_TurretMod 1.8.1 v.1.3_01
mod_ReiMinimap v3.0_01 [1.1]
mod_Backpack 1.1.0_v2-2
mod_BCIC2Crossover IBv0.06 for MC 1.1, BC 3.1.3, IC2 1.70b
mod_BuildCraftCore 3.1.3
mod_BuildCraftBuilders 3.1.3
mod_BuildCraftEnergy 3.1.3
mod_BuildCraftFactory 3.1.3
mod_BuildCraftTransport 3.1.3
mod_BuildcraftAPS 0.1.2a (MC1.1.0 F1.3.2 BC3.1.3)
mod_BuildCraftSilicon 3.1.3
mod_chocobo 1.1.2
mod_CraftGuide 1.4.0 for Minecraft 1.1.0
mod_electricFence v1.0
mod_EllianDetector V1.26 [1.1]
mod_BuildCraftZFP (Forestry Package)
mod_Forestry 1.3.0.0
mod_GardenCraft 1.0.0
Minecraft has crashed!
----------------------
Minecraft has stopped running because it encountered a problem.
If you wish to report this, please copy this entire text and email it to support@mojang.com.
Please include a description of what you did when the error occured.
--- BEGIN ERROR REPORT ef5c2e9a --------
Generated 23/02/12 19:28
Minecraft: Minecraft 1.1
OS: Windows 7 (amd64) version 6.1
Java: 1.7.0, Oracle Corporation
VM: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
LWJGL: 2.4.2
OpenGL: GeForce 9300M GS/PCI/SSE2 version 3.3.0, NVIDIA Corporation
java.lang.NoClassDefFoundError: ic2/common/IChargeableItem
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at mod_IC2_PortableTeleporter.<clinit>(mod_IC2_PortableTeleporter.java:78)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at ModLoader.addMod(ModLoader.java:234)
at ModLoader.readFromModFolder(ModLoader.java:1278)
at ModLoader.init(ModLoader.java:712)
at ModLoader.AddAllRenderers(ModLoader.java:150)
at afq.<init>(afq.java:80)
at afq.<clinit>(afq.java:9)
at net.minecraft.client.Minecraft.a(SourceFile:265)
at net.minecraft.client.Minecraft.run(SourceFile:648)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: ic2.common.IChargeableItem
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 27 more
--- END ERROR REPORT f056cbf8 ----------