bad connection? this ever happen to you?

i got a problem. im getting a hiss out of my dell speakers (pictured in between the mpc & keyboard) everytime i connect the laptop to the mixer (via the headphone jack in computer to channel 1, 2, 3 & 4 in the mixer). everything pictured below coonects into the mixer, and the mixer goes directly out to the speakers. ive bypassed the mixer and plugged the speakers into the computer and its fine. ive replaced the wires and didnt work

its always worked for me b4, but i recntly reformatted my dell, and ever since i ve been having this problem? did i evplain this ok?

any help would be appreciated.
peace

[img][img=http://img387.imageshack.us/img387/6779/treo1212050012fw.th.jpg][/img]

And this is related to the MPC2000[XL] in what technical way?

I think there is another forum more suited for this type of question.