Just an FYI… if you purchased or are using the new sixth edition of the APA Style Guide that was released in July 2009, you should be aware that it includes some errors. This article explains more about the errors and provides a link to the APA website that includes corrections for the errors. Look under the Supplemental Materials section and then look for “Reprint Corrections”.
It looks like APA has corrected the errors in the second printing of this edition. You might want to check your copy to make sure it is up-to-date.