Were any *other* log files generated? If you have debug logging (to file) enabled, the log files should be in /includes/modules/payment/paypal/logs/

The file you quoted only shows the info that was prepared BEFORE sending to PayPal.
If there are no logs from AFTER PayPal was involved, that means you have a classic case of PayPal's servers not being able to talk to *your* server ... in which case you've not got things set up properly. Here's the extra-detailed checklist: http://www.zen-cart.com/wiki/index.php/PayPal