On September 1, 2009 PayPal's Payflow Pro payment gateway will no
longer support earlier integrations. ShopSite merchants using PayPal
Payflow Pro (formerly VeriSign Payflow Pro) need to be running
ShopSite version 10 in order to prevent interruption of their service
for processing credit cards.
More information on this issue can be viewed here:
http://support.shopsite.com/KBase/questions/2518