Have heavily modified version of osc ms2.2 using 1page checkout.
Under normal circumstances, order is placed using [url removed, login to view](sim), card is charged and order posts to store perfectly.
Problem only occurs if customer enters a coupon code(ccgv).
If code is entered, payment page price is adjusted properly... customer confirms and is sent to [url removed, login to view] to finish... [url removed, login to view] processes/charges the card correctly, but then customer is returned to checkout page where they see an error "there was a problem processing your card...".
So order isn't posting properly to store when coupon code is used, but card is being charged properly at auth.net.
I'm only looking for a pro who knows exactly what to look for and can look into this now and get it done quickly.
Additional note: the only real way to test this is by entering a cc and checking out. I created a product for $.02 and use my cc. I don't expect you to use your cc, so we may have to work together a bit and I'll continue to test with mine.
Please note: I make no upfront payments of any kind. I pay in full upon successful completion. If that isn't acceptable to you, please don't bid :)