How to deactivate Adobe Digital Editions

As found on an Adobe Forum…

To deactivate a PC with Adobe Digital Editions 1.x:

1. Launch Digital Editions 1.x
2. Enter the key-combination of <CTRL><SHIFT>D (<CMD><SHIFT>D on Mac OS)
3. At the dialog, confirm that you wish to de-activate the machine
4. Quit Digital Editions

To reactivate and authorize the machine using the same or a new Adobe ID, just re-launch Digital Editions. You will be prompted to activate.

This can apparently solve a number of random issues with Adobe Digital Editions. In my case I needed it because I used the wrong Adobe ID to activate!