Well if you moved your mixer to a different room but did not move the monitor also, I would say that it may be your monitor.

I recently built a studio for a client of mine and we ended up using an older flat screen monitor. We had a similar problem with the noise and eventually found that it was the little power supply for the flat screen that was sending the noise down the firewire cable.
Wierd, but true.

I just installed a new flat screen (Apple w/digital conection) and the noise went away.

I hope this gives you somewhere to start.

Chris

You've probably got a grounding issue. Don't ask me how to solve it, because I had a similar situation and I'm not really sure what solved the problem for me. But here's what I did.

I changed the main feed outlets and power strip to other plugs on another circuit. Also, I changed the layout of my microphone audio cable and everything settled down. My house had been remodeled. The plug that was giving me problem was from the old, ungrounded AC circuit that had a plug that included a ground, but it wasn't connected to anything. The other circuit was added when the house was remodeled, and did have a true ground.

Also of interest is that I found my powered speakers added buzz, but the signal was, otherwise, clean, after I changed power outlets and the cable.

In my research, I found some solutions but they involve getting into the electrical wiring. I think there's also some power conditioning stuff on the market.

Good luck.

CC

Littledogaudio, ccool,
thanks for replying

grounding issue ey?

what's driving me nuts is that I didn't change a thing!!!
what could have possibly triggered this noise?!?!?!

if I invest in a Power Conditioner, do you think it would eliminate all sorts of noise?!

anyone with Power Conditioners, can you advise?!