I had a perfectly wonderful transaction key running successfully through the gateway (authnet). Now, no matter what tkey I use, reset, whatever, it will not work. I set up cart in oscommerce without too much problem (I'm a beginner), but I have no idea how to troubleshoot this. I have a general error at the terminal when going through the cart to make a cc charge. Do I need to start all over again? Can I just upload some new untouched files. I've looked at the files I think are associated with this and the modification dates are no different than when I set up the cart at the beginning, but the information contained inside is not the default set up info. The two files I looked at are modules.php and authorizenet.php.

What error message are you receiving? Did you search the osCommerce forums to see what they suggest?