Dave,
Apologies for the delays. We've been doing some investigation, but simply can't recreate or understand the issue you're having. The https root certificate for the Windows Live servers should be included in any PHP installation. The certificate name is:
VeriSign Class 3 Public Primary Certification Authority - G5
That's a very standard certificate for 'big' sites, and should be loaded properly. Obviously, on your site, there's issues doing that.
With that said, I was unable to FTP into your server. I'm not sure what was happening, but it was never connecting to even try authenticating.
What I can recommend to do, which should work, is edit the following file:
/libraries/joomla/http/transport/curl.php
Around line 63, you'll see:
// Setup the cURL handle.
$ch = curl_init();
Directly under that, add the following line:
$options[CURLOPT_SSL_VERIFYPEER] = false;
That will decrease the overall efficacy of *outgoing* SSL connections on your site. Data will still be encrypted, but the destination (Microsoft's servers) won't be validated against known root certificates, since the Verisign root isn't properly found.
Please test that and let me know how it goes. Hopefully, authentication will start working and get you going for now.
Thanks,
Alex