it doesn't work in 10.6 either! that is, on one om my household's computers - my MBP17 can connect easily - my mothers MacBook just gets:
"Searching after updates failed. Couldn't communicate with Web proxy server (HTTPS)."
I have rebooted, erased several plist-files - but the problem remains unsolved...?
update! - there was a weird webproxy setting on my mothers macbook, I turned that off and now it works just as it should!