OP, here. Good news, I got it to work. Vaidas3's link to [H]ard Forum showed a thread that contained a comment about using a Jmicron controlled port instead of the ICH10R. My mb has six ports controlled by the ICH10R controller and a pair through the Gigabyte SATA2 controller.
Just for grins, I plugged the 3tb HDD into one of the two Gigabyte SATA2 controller ports and the system recognized it perfectly. Even more surprising, after I initialized the HDD, I plugged it back into one of the original ICH10R ports and it still works fine. I didn't load any new drivers, reflash BIOS or anything like that.
Obviously, I'm in a bit over my head here. Can anyone explain why this is working now?