Comment 30 for bug 24250

I have seen this as well. It seems only to be a problem when you click on the 'Upgrade' button, when it does some checks before displaying the Release Notes. I can verify this by starting update-manager with ports 80 and 443 blocked on the proxy server (ie, http and https forced through the proxy), clicking 'Upgrade' (at which point update-manager freezes) and then going on to the proxy and unblocking those two ports. When the firewall is restarted with ports 80 and 443 open, update-manager continues to the Release Notes page. I can then block the ports on the proxy again and the upgrade continues as normal, using the proxy. I am guessing that there is just one point in the code where the proxy is being ignored.