Issue:
If a proxy is configured in:
/application/config/config-defaults.php
then the ConfortUpdate will fail at the point of downloading the update zip file.
Cause:
This happens because the CURLOPT_PROXY is not set in the function _performDownload defined in /application/models/UpdateForm.php
Resolution:
set the CURLOPT_PROXY in the _performDownload function if a proxy is present in the configuration file. Apply the patch below:

##Begin patch:
1023,1027d1022
if ($this->proxy_host_name != '')
{
$proxy = $this->proxy_host_name.':'.$this->proxy_host_port;
curl_setopt($ch, CURLOPT_PROXY, $proxy);
}
##End patch

Regards
Francesco Petrone (digitmaster)