Download problems:
If you paid through paypal and your download crashed, you need to go to home page of our site and click on log in, then forgot your password (automatically creates an account and will send your password to you) and then log in. That will take you to your order's page and click on view, then download

Payment problems:
When you use credit card for payment and get message:

"The card you entered cannot be used for this payment. Please enter a different credit or debit card number."

Try using another web browser and/or delete cookies and attempt to pay with PayPal gateway using credit card again.
more info here: