I saw that thread too. That's when I had my client call Authorize.net. It has happened on a few different products on my testing. I've tried two different credit cards. Then I had my client do a test and it went through. I haven't tried again myself because I just can't go there right now. My credit cards are fine as far as I know. My client even entered her info wrong the first time and the error came back as card declined. Then she did it again with the correct info and the order went through fine.
Problem is authorize.net is saying they don't see anything. But this error comes from them, not from the cart, right?