Gateway laptop - interference over speakers only when plugged into AC outlet

Hi,

I purchased a new Gateway MT6840 laptop last year for the purposes of doing DJ work with it. I've been able to get it hooked up to my mixer (with and without a 3rd party sound card, and can play music through it quite well.

My problem is that whenever I plug in the laptop to an AC outlet, I get interference over my speakers. I'm using brand new Gemini GX-1501 powered speakers. I have noticed that I do not hear the same interference sound when I just plug headphones into the sound card. The interference goes away as soon as I unplg the laptop.

I have tried plugging it into different outlets, and moving the power supply of the laptop as far away as possible - no difference.

Any ideas on what i can do to eliminate the interference? I can't do a DJ gig on just battery power....

Any suggestions appreciated!

-James