When I'm trying to redirect from paypal site to circulorural.com Firefox warns about insecure data sending. If I click "Continue" button right after it appears then everything works fine. Still if I wait for a few seconds and then click "Continue" I get an error because in this case firefox just opens the link without sending transaction data from Paypal to circulorural.com (my site). Tou can test it adding a new user / listing and paying with a paypal test account. (Now http://circulorural.com is in paypal demo mode).