Early today 11-19-2010 we have released version 1.0.1 of the Amazon Product API (APaPi) library. This release corrects 2 main bugs that were in the first official release:

Japan Domain correction – updated japan domain to .jp from co.jp
setLocale validation fix – logic corrected for false negative.

If you are using the library to query the Amazon Japan locale you will need to update to version 1.0.1 from version 1.0.