Saving chunks when clicking with Energy Sensor Kit on my reactor 
Error log:
Display Spoiler
2012-08-20 14:31:16 [SEVERE] A critical error has occurred.
java.lang.NoClassDefFoundError: ic2/api/IEnergyStorage
at nuclearcontrol.EnergyStorageHelper.getStorageAt(EnergyStorageHelper.java:15)
at nuclearcontrol.ItemEnergySensorKit.onItemUseFirst(ItemEnergySensorKit.java:30)
at aes.a(PlayerControllerSP.java:205)
at net.minecraft.client.Minecraft.c(Minecraft.java:1357)
at net.minecraft.client.Minecraft.k(Minecraft.java:1800)
at net.minecraft.client.Minecraft.x(Minecraft.java:822)
at net.minecraft.client.Minecraft.run(Minecraft.java:750)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: ic2.api.IEnergyStorage
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)
... 8 more
Edit: oh, just noticed new IC2 version. Stupid me.