Agree – this one is buggy!

For reference, he’s talking about this:
http://wordpress.org/extend/plugins/addthis-sidebar-widget/

This thread should probably be merged into this one:
http://wordpress.org/support/topic/126153?replies=1

fuzing: The URL it uses appears to be based on the siteurl. Verify that you have the correct information on the Options->General page for both the URLs there.