The reason you are seeing this error is because your secure url is having issues. You will want to verify that the global https url is properly specified and that it has an ssl installed at the location specified. To check what it is set to you will want to go to 'Cart Settings' >> 'Global Cart Settings' >> 'Global Site Settings' . Once there, scroll down to Global Https Url : and verify the information that is there. If the information is correct, there may be an issue with the installation of the ssl and you will want to check with your host.
