To get around this, just turn off “automatically select mirror” and you’ll get the nice full list of mirrors to select from. In my case, it was repeatedly selecting software-mirror.com, even though it was not up-to-date and kept failing. Switched to a Georgia Tech mirror and I was golden.
Window->Preferences->Install/Update->Automatically select mirrors-> uncheck
Help->Software Updates->Find and install...->Search for updates->Finish
(the mirror selection screen appears)
