OK I have this annoying problem and I don't know how to fix it. Every time I connect my notebook to a power source an annoying EEE noise and clipping sound comes out from the speakers. This only happens when connected to a power source. When i Disconnect it, it stops,. I tried to different laptops and it has nothing to do with operating systems. I just don't know why when I have my two 400's connected through USB this would happened? I tried different plugs seperating the cables and Nothing. It is really agrevating because I can only mix for 2 hours before the PC dies out.

To me it sounds like your power supply is going out on your laptop.
But is your plug grounded?
You say you have tryed different plugs and cables I take it that was on the 400's.
Have you tryed a different plug on your laptop?
You live in the U.S. I would take the laptop to bestbuy or one of thoes big stores and have them check it out most will do this for free.

Are you connecting the computer and the devices to the same power strip (or wall outlet)? Are you using a USB hub? If so, is it powered?

My new Acer Laptop also produces noise everytime I plug it in. I had unplugged everything to retrace where that noise was coming from just to realize that it was the Power Adapter on my laptop. Just letting you know I have that noise myself but it wasn't my CDJ-400's fault.

make sure the powersupply from your laptop is a 2 prong power supply. i used to have the same problem. i had a dell studio laptop with a 3 prong powersupply. every time i plugged it in i would get theis annoying noise from my speakers. i called dell and order a 2 prong powersupply. that was the problem. there has to be an issue with the ground..

hope this helps.