The PHP function curl_exec is disabled globally on the server.
However, you can enable this for your account by placing the following rule in public_html/php.ini :
curl_exec = 1

Then add the following rule (with the correct path) to public_html/.htaccess (if it is not already there) :
# enable subdirectory inheritance of custom php settings
suPHP_ConfigPath /home/[your cPanel username]/public_html