Checkout subtotal/grand total/card problem

I owe [login to view URL] website - webshop biult on Magento system. Recently I installed following extensions: - donations ultimate - free downloadable product - paymentsense After that it seems that grand total, subtotal and card modult show 0.00 to pay all the time. When you add product to card (or click buy now). Everything works fine when used is logged in, but as guest it looks strange and not trustworthy. All extension developers said that it is not caused by their extension so I'm looking for person who is open to fix it. It seems to be a simple issue, however, I'm not literate in coding. Please let me know if you can do it or contact for possible details. Thank you. Alan