When I try to charge a credit card in call center order, I get this error:
 
Notice: Undefined variable: r in /admin/admin_order_call.php on line 1673
 
Fatal error: Call to a member function get_value() on a non-object in /admin/admin_order_call.php on line 1673

Hello Alex,
 
Could you please contact our Support Centre with access details to your site if your problem is still actual?
 
ViArt Support

I had exactly the same problem, but I found that by excluding custom fields from the order form it didn't throw the error.
 
Now I just get error 10747 Invalid Data - I wonder if that is because I am hooked up to a test PayPal web pro account?

To take this forward a little it appears that this is a payPal error and that they aren't getting the IP address from ViArt:
 
 
This error occurs when you pass an invalid IP address as part of your Direct Payment request. PayPal requires you to capture the the buyer's IP address and send it as part of the Direct Payment API request. The IP address must be in a format such as 123.456.123.456 (e.g. IPv4 format). IPv6 formatted IP addresses are currently not supported.
 
Is this a test environment problem or a ViArt problem? Hooked up to PayPal sandbox.