I have (almost) the same problem. Any of my machines (compressor, exractor, generator, macerator) are not making any sounds when working. Only when on low EU I hear the infamous sound, that machine have stopped working due to out of power.
I have installed MC Forge 4.1.1 to minecraft.jar and IC2 (to mods dir ofcourse).
I also have been using other mods like BC, Forestry, Railcraft. Will try to remove them and test with only IC² present.
This occured when running local world, will try in "SMP".