Thanks for the help! Turns out it was Flans mod DX. Favourite mod as well.
Oh well, at least I can go pew pew with a laser now xD
Edit: Hold on! it crashes again
Crash report, again:
Mods loaded: 28
ModLoader 1.2.5
mod_CodeChickenCore 0.5.2
mod_NotEnoughItems 1.2.2
mod_Armor 1.2.5
mod_MinecraftForge 3.1.3.105
mod_Soundpacks v1.0 by Crazyputje and Xamio (XamioStone)
mod_TF2Sentry 1.2.5 by pitman-87
mod_TF2Teleporter 1.2.5 by pitman-87
mod_TF2Dispenser 1.2.5 by pitman-87
mod_ReiMinimap v3.0_04 [1.2.5]
mod_BuildCraftCore 3.1.5
mod_BuildCraftBuilders 3.1.5
mod_BuildCraftEnergy 3.1.5
mod_BuildCraftFactory 3.1.5
mod_BuildCraftTransport 3.1.5
mod_AdditionalPipes 3.0.9 (Minecraft 1.2.5, Buildcraft 3.1.5, Forge 3.0.1.75)
mod_BuildCraftSilicon 3.1.5
mod_CraftingTableIII (Beta1.2, MC1.2.5)
mod_IC2 v1.95
mod_PigbearLaser 1.4
mod_MAtmos_forModLoader r12 for 1.1.x
mod_Zeppelin 1.2.5.0.30
mod_Railcraft 5.2.0
mod_RedPowerCore 2.0pr5
mod_RedPowerLighting 2.0pr5b1
mod_RedPowerLogic 2.0pr5b1
mod_RedPowerWiring 2.0pr5b1
mod_RedPowerWorld 2.0pr5
Minecraft has crashed!
----------------------
Minecraft has stopped running because it encountered a problem.
--- BEGIN ERROR REPORT acad6b97 --------
Generated 05/05/12 20:06
Minecraft: Minecraft 1.2.5
OS: Windows 7 (x86) version 6.1
Java: 1.6.0_31, Sun Microsystems Inc.
VM: Java HotSpot(TM) Client VM (mixed mode), Sun Microsystems Inc.
LWJGL: 2.4.2
OpenGL: GeForce G 105M/PCI/SSE2 version 3.0.0, NVIDIA Corporation
java.lang.NullPointerException
at ic2.common.TileEntityReactorChamber.onCreated(TileEntityReactorChamber.java:33)
at ic2.common.TileEntityReactorChamber$1.tickCallback(TileEntityReactorChamber.java:22)
at mod_IC2.OnTickInGame(mod_IC2.java:1377)
at ic2.platform.Ic2.onTickInGame(Ic2.java:347)
at ModLoader.onTick(ModLoader.java:1102)
at EntityRendererProxy.b(EntityRendererProxy.java:22)
at net.minecraft.client.Minecraft.x(Minecraft.java:869)
at net.minecraft.client.Minecraft.run(Minecraft.java:747)
at java.lang.Thread.run(Unknown Source)
--- END ERROR REPORT 67b28cdd ----------