Here is a problem that probably exists in different scenarios I guess. This happened in my case.
I tried to activate Windows Live OneCare subscription online when traveling in another country than my credit card is issued in. I couldn't even purchase a new license if I wanted to. The website sees from the IP that the country you are in and the country of your credit card does not match and denies you to purchase.
All I got when I tried was a website with this information.
Review details for your location
The selected plan is available, but the plan details may differ in your location. To review the plan details for your location, click Continue
If you get this message more than once, report it as a recurring problem.
Lesson is that make sure you don't need to update the subscription when you travel to other countries.