Record it, add a little phaser and reverb, and put out an ambient/drone album?
Seriously though, check the obvious thing first - if you unplug the Profit from your A/D does the noise stop?
If so, check the outputs of the Profit through a different monitoring system - maybe there is some weirdness going on there that you hadn't realized.
If that's not it, then maybe you really do have a feedback loop. Does the Profit 8 have audio inputs and if so have you been sending a signal from your computer to it recently? The weird thing about external instrument is that the audio inputs are always "on" regardless of whether or not a MIDI clip is playing. So if you're still monitoring even part of a signal being sent back to the Profit there could in fact be a feedback loop if the patch on the Profit is also passing the audio inputs back to the outputs.