I used the extension manager to download an extension. In this case Lufa, if that matters.
I logged in. The login window disappeared. Then nothing.... for > 1 hour while I was hardwiring ...
Then Killed AS and tried again.
This time there was a dialog window asking me to accept the terms for installing Lufa.
I have a suspicion that this dialog is what made it necessary to kill AS. I have discovered before that it can hide a dialog. And it will not be possible to move or minimize AS to make this dialog accessible.
Is this a known behaviour? And if so, is there a way to get to this dialog. (Alt-Tab does not do it.)