Tuner can be heard through other inputs

are you sure it's not RFI? some people get radio stations' signal in their systems. I assume you've disconnected the tuner to check this, but if not...

Try everything else listed above, but if you can't get it to stop, this is what I heard just this week-end from a competent designer/builder:

Naim tells their dealers to only demo with one unit plugged in, as this cross-talk is inherent in their grounding/design method.

Now, for you Naim folks, I like the sound, but if this is a problem, the unit is probably NOT defective. If my guy is right, then your unit is just working the way that Naim components work and is okay. I hope one of the other suggestions is helpful, but if not, don't freak out, it';s just the way it is: anything else turned on and playing is going to bleed through at a low level.

Just what I heard. Please don't crucify me for passing it on.

You could unplug the rca's from the Naim but try this first. Have the muting on and put the dial where there is no station.

OK,
Just figured out that if there is a component plugged into each input either side, then no problem. As a test, If I only hook up a pair of interconnects with no component, then bleedthrough still exsists.

I think JEA48 hit on it by suggesting shorting plugs. That would simulate (to the integrated) a component being plugged in.
Jeffb your theory may be true as well. Naim does grounding is a bit different through DIN.

Problem solved.
Thanks Again

Have you tried running the system with only one source input plugged in to teh amp at a time? That might give you better sound than using shorting plugs.