I did a search online for before_process oscommerce and I found an old forum entry that told me that that payment before_process() function gets called in the checkout_process.php step. It also stated that the call to that function needs to come after the place where $order_totals_module is defined. So I looked at my version of checkout_process and the call to the payment before_process() function was before the $order_totals_module.
Since I had not initially modified the checkout_process.php file I overwrote it with the version that came with the CCGV addon. That was my mistake. I didn't think that it would be altered other than for the CCGV module. Anyway, it now works for my coupons and it works for points redeemed. The only thing that I didn't test yet is the gift vouchers.
I sincerely appreciate the effort that you put into this request. I hope that I didn't bother you too much.
