Aahhh yes, what David said!!
FYI I use a 12V 12A Powertech switchmode supply to my Kendrick dew heater which in turn supplies 12V to my Robo. All of my cables run in a bundle to the pier too (incl a 240 supply to my camera brick on the pier) without any noticable effect. Perhaps filtering electronics or sensitivity to EMI in the camera (SBIG vs FLI) is coming into play too(??).
As others have said, I would firstly separate the cables as far as possible to see if proximity to the camera USB is an issue. Then I'd run from a battery. One of these will almost certainly eliminate the noise.
Congrats on the Robo BTW - it sure improves the whole imaging experience. Try FocusMax too - it's very good and free.
Cheers, Marcus