This is being caused by a php bug when used under IIS. see this past for details:
https://bugs.php.net/bug.php?id=43977
using phpinfo() i see your php version is 5.2.17
either, change the hosting account to a Linux account using Apache, or have the host update the php version.
NOTE: where you are using shared hosting, you will need to pass the cart contents to the secure server from the c art page.
see this page for more details:
http://www.webassist.com/tutorials/Secure-Socket-Layer-SSL-and-eCart-sites