Loud hum in one channel

I just finished setting up an Empire 598 III turntable, and, unfortunately, am getting a fairly loud hum out of the left channel, which will happen on the right when I switch the leads. I am using a Sumiko Blue Point, and the ground wire is connected. Any help on solving this would be greatly appreciated!
when you say it moves when you "switch leads", do you mean when you swap interconnects from the table to pre, or when you swap cartridge/headshell leads? I assume you mean the former, and in that case I would suspect a poor connection at the headshell (ie as the easiest to fix issue), if it's not that, then it could be something in the tonearm wiring. I would start by double checking a good fit of your cart/headshell connects.
Do you get the same hum when operating another piece of equipment like a transport? If so, it may be your processor. I had the same problem and it turned out to be a grounding issue. I had to plug the left channel mono amp into a three to two plug converter, then into the dedicated PS Audio receptacle. Problem solved. Just food for thought. If I switched IC cables the hum came through the other channel so it became obvious that the problem was with the processor, not the transport or mono amp. At least that was my experience. Maybe it is helpful.
The hum switches when I swap interconnects from the table to the preamp, and the noise only happens when I am using the preamp setting for the turntable; in other words, it does not happen with the CD players. BTW, the noise is present even when the TT is off, and with JUST the ground wire attached and not the interconnects; is that weird???
Hurricane: You indicated that the noise is present even when the TT is off with just the ground wire attached (not the ICs). When you hear that hum is the preamp set to TT? What if the preamp is set on "CD" for example. With the TT off and the CD off - do you still hear the hum? What if you disconnect the ground wire as well when the TT is off - still got the hum? I'm still a bit suspicious of a grounding issue in your pre amp.
Puerto, yes the hum is present when the preamp is set to TT but not on CD or AUX. I will disconnect the ground wire as soon as I get home and report back. Thanks for your help!
Here's a follow-up: Disconnected TT and ground wire, and noise like jet engines coming out of both speakers, more so on the left, but only on the TT setting, not the CD. Re-connected the Empire, and very noisy on the left channel, not so much on the right. Finally, I connected my Funk TT and also noisy, although nowhere as much as the Empire, and more so on the left. When I connected the Funk TT to the CD interconnects, I get no noise.
The phono amp in the pre-amp was installed when I bought the Prima Luna pre-amp. Is this the culprit?
Sure sounds like the phono amp in the pre-amp is indeed the culprit. That would need to be checked out by a professional but I would sure start with that. If it was the pre amp itself you would probably be getting hum/noise out of any setting (CD, AUX, etc.). Let us know. Hope it isn't too expensive!!!
Thanks, guys. You know, I was never enamored with that phono preamp that was installed, and I wonder why it took the Empire TT to bring out all the bad in it, when the Funk was playing not too badly. At any rate, I will shop for an external phono pre-amp and try it that way. I hope that is all there is to it.