Authorize.net problem

[cardsup]

We are using Authorize.net as a processor on our web site

 

Most times there are no problems, however recently we got many complains from customers who can not place an order. The way the site is set up, on checkout the client goes to your site:

 

https://secure.authorize.net/gateway/transact.dll

 

where the problem seems to be occurring. Here is a description of the problem one of our clients gave us:

 

"This is what happens when I try:

 

- I have my shopping cart, and I click on "Checkout"

- This brings me to "Payment Information"

- I click on "Select Authorize.net" and then "Continue"

- This brings me to "Order Confirmation" where I click "Confirm Order"

- The next page appears to be the authorize.net page, where I enter all of the credit card information: https://secure.authorize.net/gateway/transact.dll

- I click on "Submit Transaction"

 

Yesterday I believe after I did this, I got some sort of confirmation page. Today, after I click "Submit Transaction" I am brought back to the "Payment Information" page where it prompts me to begin all over again.

 

This new order is also not in my order history, so I'm assuming it did not go through."

 

What could be causing the problem is and how it can be fixed?