C'mon, don't feel bad, Lee. You're still top notch in my book. Some folks aren't just versed in the ways of the Penguin. I'm not - yet.
But I did get that Ubuntu box to finally log into the network. Turns out, for some reason that I've not understood, I had to have the machine on the local subnet of a Domain Controller to get it to log in. It wouldn't work, traversing the WAN, even though the DC would fully resolve, to include the SRV records and MSDCS zones. I've had Windows machines be able to authenticate initially across the WAN, so there's something in my set up that was not allowing that to happen. A very odd problem.