[LAU] RF noise suppression?

I'm using a FOcusrite Saffire pro 26 I/O with ffado, jack, and Ardour to make multitrack recordings of live concerts, to my emachines M6810 laptop running ubuntustudio. I'm plagued by noise that sounds to me like RF interference from the laptop, getting into the audio portions of the interface. It's most obvious when I'm at home trying to mix down my recordings, as its almost constant in my monitors and most noticable in a quiet room, but it also manifests itself sometimes during shows, showing up on the input lines to the interface, which are plugged 'half-way' into the FOH mixer's channel inserts, so it invades the PA and the performers' monitors. WHen that happens, I've no other choice but to abandon the recording and shut down the laptop. Has anyone else encountered this problem? Got any suggestions how to filter it? I'm going to try some ferrite cores snapped around the firewire cable first. Anything else I might try? -- Rick Green "Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." -Benjamin Franklin "As for our common defense, we reject as false the choice between our safety and our ideals." -President Barack Obama 20 Jan 2009