Yellow border + unable to click!

OSX 10.9.5

I have been editing a single track recording with no difficulties, then suddenly there is a yellow border around it and I cannot click ANY part of the window, not just the track, without hearing an OS noise. “undo” doesn’t work, I can’t save anything, and almost all of the menu options are greyed out. Help!

A yellow border round the current track is normal.
This is on Windows, but you can see a yellow border around the upper track, which indicates that the upper track “has focus” (it’s the “current” track):

Is that what you are seeing on your machine?

What’s the noise?
What were you doing when the problem started?
How many Audacity windows are open?
Is there an Audacity dialog screen open anywhere? (perhaps hidden behind the main Audacity window?)

The noise is the typical Mac sound when something can’t be clicked. I was clicking on generate > silence, but I may have clicked tone by mistake.

I don’t see any dialogue box. Only one audacity window.

Please tell us what version of Audacity you are using (all three numbers). Right-click or CTRL-click over > Get Info… will tell you.

If you do Audacity > Quit Audacity, do you get an option to Save Changes? If you press Cancel, do you get back control of Audacity?