ECart 4.1.1 / Authorize.net dies after when final form is submitted
As above, using eCart with Authorize.Net. Recently (started in the last few weeks), about 50-65% of customers are reporting that after submitting the order from the final review page, they get an error:
Transaction Not Completed
Your transaction could not be completed due to an error. Please contact the Webmaster for more information.
Return to the Store.
However, the credit cards are valid (when we process them manually from A/N, they go through). Why is eCart failing here?