Tonearm/cartridge is a theramin. Suggestions?

I'm vexed. I just installed a musical surroundings Nova II and it's partnered with a Clearaudio Maestro v.2 cart on a rewired Rega 303 arm. It really sounds great, but there is quite a high pitched hum. The sound is exactly like the sound of distant speed boat propellers from underwater. I remember swimming in a lake in the summers of thirty-five years ago and it's uncanny how the sound of this strange tonearm/cart phenomenon brings me right back!

Any way, it's like a theramin because if I just wave my hand near the cartridge, the sound increases in gain by at least 6 dB but the pitch doesn't. Removing the ground wire from the Nova phono preamp dramatically increases the gain of the sound. I did not have this effect when I was using the on-board phonostage of an integrated (now sold). 

Audiophile community: HELP!

thanks,
Oran.