There is a thread on a related subject here:
http://amazingcharts.com/ub/ubbthreads.php/topics/70667/Re:_New_Security_Measure_Probl#Post70667
I don't think my problem is a "security measure". I think that AC is trying to block me from upgrading when I have less than a month left on my "guardian angel" support and maintenance contract.
Basically, I would not attempt an upgrade unless you had pre-arranged an appointment with AC to be of assistance at the same time.
I've never had a problem with upgrades in the past. They are easy to do and have always gone off without a hitch (but I have had problems with the upgrade being buggy).
I'm not going to schedule a meeting with support just to perform an upgrade. They're on the east coast, I'm on the west, making it near impossible to correlate at time, as they don't like to perform support outside of business hours. And the same applies since I perform my upgrades on the weekends so I have plenty of time to ensure things go smoothly, and so I can test the installation for a couple of hours before I have to use the software for real work.