Been having this problem for nearly a week now and PayPal technical support is basically lost and of not much help.
I'm running PayPal Advanced, when a customer (or myself) checks out of the store with a credit card, they get a pop up saying 'payment declined, please try again'. The problem is, is the payment actually goes through to paypal but the order ends up canceled in the orders in the admin of magento.
It's an odd problem, as it started happening about a week ago, but it does happen with EVERY order. Doesn't look like it's either user error, nor is it a problem with one specific product.
As said above, I've called paypal on this and they say my account is setup and integrated fine, but they can't find the issue. They thought it might be a silent post issue, but they haven't confirmed that yet.
I have debug mode on but have no idea what i'm looking at in the file - nor do i have the knowledge on how to try to see what other error might be happening between the submitting of info and the decline notice.
I was running 184.108.40.206 and have since moved to 220.127.116.11 and upgrading didn't solve the issue either.
I also tried what was posted over here, but that didn't work either: http://www.magentocommerce.com/boards/viewthread/991120/
Any help or insight would be wonderful