It seems like a publisher id is required for analytics stats in addthis now. Can you please add the publisher id to the default settings (via admin settings form) so that analytics data is linked properly to an account? I haven't tested this and I'm just going on the following documentation: http://www.addthis.com/help/default-code
pubid being the relavent paramater that needs adding. I couldn't find any references in the addthis documentation to the username parameter so I'm not sure if its required anymore.