Many people have reported the error in their online statements for May 2010 about an exchange error that affects those in Asia. Instead of the prevailing currency exchange rate that is used, the online statements shows a 1:1 exchange rate for the US$ to the currency of the adsense publisher's country.
So far, many people have highlighted this to Google and it seems that the problem will be rectified only after Monday due to the US holidays.
It states that though the online statements show the 1:1 exchange rate error, the checks that will be issued will be based on the correct exchange rate.
It does not seem that this is the first time that the exchange rate error bug has hit. A simple search on the internet revealed that the bug was first reported in 2008.