When Discover is started from Updates Available it takes a while - sometimes several seconds - to collect sizing information for the available updates and display it. There appears to be a timing issue whereby if the Update button is clicked during this time the application hangs and does not display the password dialog. If I wait until the information has been collected and displayed it never hangs. I've seen this behaviour on 2 Neon and 1 Kubuntu systems, all with current updates. I've sometimes had the password dialog open behind the main screen, which is then blocked. I'm not sure if this is the same issue as most times I'm not able to find the dialog.
I've experienced this a few times. Need to reproduce it in gdb and get a stack trace.
I'm pretty sure this is related to 397759 and 397938. Closing *** This bug has been marked as a duplicate of bug 397759 ***