I recently upgraded to 1.5.4 from 1.5.1.

I forgot to test credit card payments before I went live (I did test paypal). Unfortunately it isnt working. When (as a customer) I hit the continue button to confirm my order, I get:

An unknown response null: :text/html; charset=utf-8: :SyntaxError: JSON.parse: unexpected character at line 4 column 1 of the JSON data was received while processing an ajax call. The action you requested could not be completed.

I am not sure where to look. I use the Authorize.net (AIM) module.

Any help would be great.

Linda