There are some countries that simply do not like Google or they simply don't get along with Google. If you are in one of those countries and you try to access Google AdSense or possibly other properties, you may see a message from the provider.
A WebmasterWorld thread has a copy of that message. Here it is:
Unable to access AdSense homepage
A connection has been established between your current IP address and a country sanctioned by the U.S. government (for more information, see http://www.ustreas.gov/offices/enforcement/ofac/ ).
We're unable to grant you access to the AdSense homepage at this time.
I personally never saw such a message, so when I saw a thread about it, I found it interesting.
Forum discussion at WebmasterWorld.