Prefix for virture Add to Cart button will not work.

[fdimah]

I have a site.  http://www.parisfleamarket.biz with VirtureMart 2.0.2 installed.  I want the URL to be this.  http://shop.parisflea.com  I have the both domains.. and have http://shop.parisflea.com pointing to the correct path.  When you try to add something to the cart at http://www.parisfleamarket.biz the items is placed in the cart.  If you try to add something to the cart at http://shop.parisflea.com it does nothing...

Please help.

mark