mp_cart_form appearing twice on page

I have version 1.0.4 of Marketpress activated on a multisite install.

When I go to the shopping cart page the mp_cart_from is appearing twice.
Once in the page background above the header, and once in its usual page container place.

On another site using MP 1.0.3 I'm not having the same issue, even though using the same theme (Thesis)

Can anybody please shed some light?
thanks in advance