One of the payment methods that Google offers their AdSense publishers is via Western Union. Well, this month, about 5% of those payments were accidentally declined.

Google announced this in their Google AdSense Help forums saying:

It only impacts those in the following countries:

Egypt
Saudi Arabia
Cambodia
China
Indonesia
Malaysia
Nepal
Pakistan
Singapore
South Korea
Taiwan
Thailand
Vietnam

At least you are in good company, if you were impacted by this.

Forum discussion at Google AdSense Help.