Well, heck...
I installed the CVV2 module and then removed it because after testing with dummy CC's and even my own CC#, I could not get the test orders to go through. I would get the same "Credit Card Error!" on the confirmation page. I tried setting the CVV2 requirement to "false", but when I did that, the entire payment information/CC info entry fields would disappear entirely from the checkout process.
Now, after removing the CVV2 module, I get the CC info entry fields (just name, CC#, and exp. date), but no matter what I enter, I get the same message, "Credit Card Error!" - unfortunately, that's all it says. Any of you smart types know what might be going on here?
Thanks in advance for any help.