I understand you are having a problem with your checkout and I would like to help you resolve it. The errors you are reporting with divide by 0 is not something that I have encountered myself on any eCart pages.
You can confirm that when you checkout with credit card that the transaction is occurring but instead of going to the checkout success page like you should you are getting this error on the confirm page rite? If so it seems that there might be a problem with one of the values that is being used on this page, probably around the line that the error is reporting.
To help you get this resolved I would like to see a copy of your confirm page that is causing this error. Please post back with this page in a zip archive minus the sensitive details like your PayPal login info and I will check it out to see if I can spot the problem quickly.
It also seems that you are unaware of the support hours and reply time policy, it is not that no one is here or cares, it is just that we work Mon-Fri 9-5 Pacific time. Your first post was made Friday afternoon and is being responded to on Monday morning, well within the stated support policy. This information can be found at the top of the forum under Hours and Policy.