Hi, just my 2 cents : i've had the same problem with my MB (digital noise when USB cable connected). I've buy a MIDI-USB adapter (m-audio midiport) to connect the brute through the MIDI cable but -!surprise!- the noise was still present, now when the midi cable is plugged in the brute (a little less maybe but still present).
Now, i've simply inverted the MIDI cable from the MIDI adapter to the MB and the noise is gone (!!!!!)...
Maybe is the midi cable that have some sort of ground ??
The problem is solved for me, before i've tried ALL the tips read here and in a lot of other places (ground loops, hub usb, balanced cables) except for the DI BOX, nothing have worked.
Only solution for me: USB/MIDI adapter and the correct way to the cable.