Duplicating link in tweet button on a website


I’m doing some maintenance for a website and for whatever reason the tweet button on this particular website does not generate the correct link. Go here to see the problem: http://bookstore.inspiringvoices.com/Products/SKU-000620288/Arrows-of-Light.aspx, click on the tweet button, when a window pop up it will generate “Arrows of Light - David Schneider : Inspiring Voices http://bookstore.inspiringvoices.comhttp//bookstore.inspiringvoices.com/Products/SKU-000620288/Arrows-of-Light.aspx via @IVPublishing”. There is two url instead of one, strange thing is the other website is working just fine http://bookstore.authorhouse.com/Products/SKU-000409636/da-nang-postscripts.aspx, both are using the same code in the html. What could be the problem? Could someone help me?