payment will not go through

After adding to cart, and checking out, and entering in my paypal login and clicking pay now, I get this from paypal:

This payment cannot be completed and your account has not been charged. Please contact your merchant for more information.
Return to merchant and try a different payment method

We are not able to process your payment using your PayPal account at this time. Please return to the merchant’s website and try using a different payment method (if available).

Is this a simple cart issue, or do you think it is a problem with my paypal account configuration? I’ve been using this plugin for years without an issue… just started happening in the past week or so. Thanks!

http://wordpress.org/plugins/wordpress-simple-paypal-shopping-cart/