I'd install your mod and i had this error log.
Code
Mods loaded: 4
ModLoader 1.2.3
mod_IC2 v1.81
mod_MinecraftForge 1.4.0.57
mod_ModLoaderMp 1.2.3
Minecraft has crashed!
----------------------
Minecraft has stopped running because it encountered a problem.
--- BEGIN ERROR REPORT 30951d59 --------
Generated 20/03/12 15.13
Minecraft: Minecraft 1.2.3
OS: Windows XP (x86) version 5.1
Java: 1.6.0_30, Sun Microsystems Inc.
VM: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
LWJGL: 2.4.2
OpenGL: ATI Radeon HD 4300/4500 Series version 3.3.11318 Compatibility Profile Context, ATI Technologies Inc.
java.lang.NoSuchMethodError: ic2.common.ItemIC2.setNoRepair()Lym;
at ic2.common.ItemIC2.<init>(ItemIC2.java:27)
at ic2.common.ItemResin.<init>(ItemResin.java:24)
at mod_IC2.load(mod_IC2.java:274)
at ModLoader.init(ModLoader.java:890)
at ModLoader.addAllRenderers(ModLoader.java:186)
at aho.<init>(aho.java:79)
at aho.<clinit>(aho.java:9)
at net.minecraft.client.Minecraft.a(SourceFile:267)
at net.minecraft.client.Minecraft.run(SourceFile:650)
at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT 65dc680c ----------
Display More
I'd the same with redpower2 and buildcraft.
Sorry for my bad english, I'm italian.