I received a dreaded "cURL error: Unknown SSL protocol error in connection to secure.authorize.net:443" when setting up the Authorize.net payment gateway for use in a Drupal Ubercart store recently. Oh noes! Here's how I fixed it.
Find the module ubercart > payment > uc_authorizenet
On line 558 (your mileage may vary) I added:
curl_setopt($ch, CURLOPT_SSLVERSION, 3); // Force SSLv3 to fix Unknown SSL Protocol error
Goodbye sweet, sweet error. I barely knew ye.
Christina R., Owner StressMonkeyGuru.com
John did a wonderful job redesigning my website in a way that worked within my budget and created a result that is both impressive to look at and highly functional. He was a pleasure to work with!