Authorize.net error logs are nowhere to be found,..? and transactions not...

[DrByte]

I am having a similar issue with my new site using 1.5.3. It goes along fine until you hit SUBMIT. Then the layout of the site falls apart and it gives a generic error - Step 2 of 3 - Payment Information
Error There has been an error processing your credit card. Please try again.
No error number given.

Authorize.net then sends me an email saying
Response Code: 3.
Response Text: This transaction cannot be accepted.

Results Received back from Authorizenet: Array
(
[x_response_code] => 3
[x_response_reason_code] => 99
[HashMatchStatus] => PASS

See post #7 here: http://www.zen-cart.com/showthread.p...s)-with-v1-5-3