fishmonkey wrote:it's almost certainly a feedback loop in your routing.
i've never used the Saffire Mix Control but i just had a quick squizz at it. unless i'm mistaken, DAW 1 and DAW 2 are the channels that you have set up as main outs from Live, i.e. your L/R master channels. i bet that in your Ableton routing your return channel from your external effects is going to the Live master; from there it goes to your DAW 1/2 channels which you've got routed not only to your monitors, but also out through the analog output going to your effect. feedback loop.
in other words, i don't think you should have DAW 1 and DAW 2 routed to all your hardware outputs. i would think that DAW 3 should go to output 3, DAW 4 to output 4, etc...
you were right, i had one of the outputs of saffire mix going back into one of the inputs macking feedback.
all sorted now, i can work again xD