_Brian - you have solved the issue!
I was unaware that subsequent to establishing new "Directory Servers", you also had to go and assign new Authentication Servers to the AD Admin users. Once I did this, I was able to login to the console using my AD credentials.
Now, for some reason, if I click the "Test Account" button on my "Edit Administrator Properties" dialog, it fails.
However, I CAN login to the console using my AD credentials and it is working. So, I'm not going to worry too much about that "Test Account" button.
Thanks to all for your advice and assistance - I can move forward now!
Randy