Yo Michael Lafont:
You say that the other cartridges work just fine in this setup, but the $umiko cartridge shows up out of phase and in mono, rather than stereo, when using your test record. Frankly, I'd go back to the dealer and tell him or her about the problem. I am assuming that your speakers are correctly wired and that you are following the color code for the cartridge wires. If your amp or your speakers were wired incorrectly, the same problem woud show up with other carts and other turntables. But I would check one thing. Compare a good headshell with the Sumiko headshell and be sure that the color code and the pins on that shell are identical with the color code and pins on the good shells. I would also take a close look at the wiring and pins in the Sumiko shell and be sure that there isn't any stray contact between unrelated wires.
Then I would get a DVM and measure between the right signal pin on the cartridge and the right ground pin on the cartridge. Be careful, and just hold the meter on the pins long enough to get a reading. You should get continuity between these pins, and there should be no continuity between these pins and either of the pins for the other side. Same thing is true on left side. There should be continuity between the left side signal pin and the left side ground pin. But, there should be no continuity between either left pin and either right pin. If these measurements are all correct, then you have a cartridge that is internally miswired with the wires for one side misplaced. Sumiko has bungled the job. There is a risk that the fine wires in this moving coil cart won't take the current from the DVM, but you can make this decision. If you don't want to test, I'd take the cart and the turntable to the dealer and tell him to fix it, or send cart back to dealer and ask for an exchange and see if new cart is equally bad. You can also ask the dealer if you can test cart with a DVM.
Now take either the right side or the left side and reverse the signal and ground wires and see what happens. If the cart now works right, take it back, or send it back and scream and yell. Sumiko, or the dealer, should make good on a bad cartridge. My experience with lowly Shure is that they are real good about fixing their mistakes, (and they have fixed my mistakes, too) Sumiko, the pride of Japanese high end manufacturing, should be at least as good.
And good luck from the old guy firmly mired at the way low end,