I constantly get the message "Checksum mismatch" when processing credit card payment. Can anyone help!!!!!!!!!

We are having the same problem. Have you found a solution yet? Thanks in advance for your reply.

I am having this problem, and it's an important retail Saturday with no one to call for help. Yet another quickbooks (they only let you choose one merchant service) help issue. If anyone can just explain checksum mismatch, I'd sure appreciate it.

luby