Thanks for the response. I had done this (by coincidence), but not sure about the IPv6 issue, though. I am using Mtn Lion, so that is not an issue.
As I was messing between plugging ethernet directly into my computer and trying to get my old router re set-up, I noted that the old router did not get recognized by the Airport Utility until I turned WiFi back on (I turned it off when I plugged ethernet directly into the computer). Althought AU recognized my old router, it still did not see the new router (still slow blinking amber light).
Then I noticed in the Airport icon in the toolbar that the new router was showing up there (under Join Other Network or Create Other Network). Once I selected it there, then it showed up in AU. Not sure why it worked this way. I have had 2 prior Airport Extreme Routers (and 2-3 Airport Express) and they all get picked up in AU when originally plugged in.
Anyway, it seems to be working fine now.
Thanks once again for your input.