for trouble shooting, create another cart display page.
when you add the cart display manager, on the second step, set it to show all columns, and on the third step, set it to show the Discounts, Taxes, Shipping, and Charges individually.
this will give more information on what is actually in the cart and triggering.
also if you could send a copy of the cart object file from the WA_eCart folder, that would be helpful.