Who can help me with a ghost in my system

I have a McIntosh MX135, Marantz DV-9500, Pioneer Elite PDR-19RW and a Linn Ikemi. When no music is playing I get a 'high pitch squeal, almost a ringing squeal, not real loud' heard through the tweeters. This can also be heard between tracks when playing music as well. But, it is only when the pre-amp is switched to the 9500 or the PRD19 but not the Ikemi. The Ikemi is dead silent. This squeal occurs at 25 on the volume setting out of a possible 99. If I disconnect either the Left or Right output on the 9500 or at the MX135 input, just one cable left or right doesn't matter, it drops to dead silence. The cables on the Ikemi and 9500 are Cardas Golden Reference, Pioneer is Audio Magic Excalibur in and out. There is one other ingredient here. Both the 9500 and PDR19 have 2 prong A/C power plugs while the Ikemi is a 3 prong. I have tried ground the 9500 to the MX135 through chassis screws as well as the 9500 to the Monster Power conditioner, no change
I could use some advice from the AG alumi, I hav erubbed a bald spon from scratching my head on this one.
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The Mac has both balanced and unbalanced inputs. I assume you are running balanced interconnects. Have you tried switching to unbalanced RCAs between the Mac and the 9500? The reason I ask is that I wonder if you are observing a fault in the Mac, and the unbalanced and balanced inputs have somewhat different circuit paths that may avoid the fault. I'm just poking around trying to find a cause -- this is a toughy.
Jameswei- I am using RCA's since the marantz doesn't have balanced out puts. That thought crossed my mind as well. I spoke with Marantz this AM and he suggested I try plugging the 9500 direct in the same outlet as the Mc. Right now the Mc is direct into a PS Audio Ultimate Outlet and the 9500 is into a Monster HTS 5000. The saga continues. Thanks for your response though.
I bet the AudioMagic IC's, being a ribbon might not be grounded? or shielded either? the Cardas Gold ref is both. Switch the Ic's and see? The AudioMagic might work with the Ikemi anyhow(as its grounded), but you might have both a goofy ground issue (even if grounded by the nuetral ac prong), and a RFI thing(no shielding on the IC's or Ac cables) with the 2 prong cords, and no shielding in the IC's, and the ribbon Ic's might not even be grounded. I have found a few ribbon IC and power cords to have goofy ground issues, and generally no shielding. In a clean environment they probably sound better this way.

Just a thought or 2. Its a toughy.
Another ingredient to this story is. I spoke with a local rep where I purcahsed the MX135 and he stated from my decription that the noise sounds like a "digital bleed" and not a RFI/EMI or ground fault. Does that make sense? It does to me. I just gotta figure out if the Mc is over sensative or the Marantz has a problem. Still looking for help.