I swear it was there!!! I checked...repeatedly (well several times anyways!)
In resolving this ...I found a quirky anomaly in AX2012 that I had expected that it would have caught. I looked at the Account Structure that had my account and I looked at it several times to validate it...and sure enough ...it was in the range that I had specified and my account was in an account structure.
Yet...the issue persisted and I looked again...and again.
Finally...I caught it! The account structure had a long list of ranges and where it should have said ...
25850..25855 ... it said ... 25850.25855
...and yet AX2012 had allowed me to validate and activate it (with a SINGLE PERIOD) - which is invalid.
Once I edited that...the issue quickly disappeared.