As near as I can tell, this problem occurs any time you try to sort your description keys.
Basically, the top line of the Desc Key Editor in Panorama view is broken. If you try to use it, it won't do anything useful. The "Edit..." option is broken - there is no way to change more than one Desc Key at a time. There is no way to change the sort order of your keys - if you try, nothing will happen, and the next time you try to "Edit Keys", the editor will be mostly empty.
A royal PITA. But at least now I know how to avoid trashing the Desc Key editor completely - don't touch that top bar!