I believe i found a solution to the problem as it now works for me on a win2008r2 box.
1. download the pem file from http://curl.haxx.se/docs/caextract.html and rename it to curl-ca-bundle.crt
2. copy it to the c:/windows directory
3. add the following line of code to class-http.php in your wwwroot/wp-includes directory, where the other group of curl_setopt calls are made. around line 1080 on my version of the file.
curl_setopt($handle, CURLOPT_CAINFO, ‘c:/windows/curl-ca-bundle.crt’);
you should be right to go.
