This error is appearing because the PayPal profile is set to only accept payments from encrypted buttons. If you are using our system, then the payment process will be interrupted and that error will display.
To turn off this option:
1. Log in to your account at https://www.paypal.com/ by entering your email address and password in the Member Login box
2. Click the 'Profile' subtab
3. Click on the 'Website Payment Preferences' link in the 'Selling Preferences' column
4. In the section titled 'Encrypted Website Payments' select 'Off'
5. Click 'Save'