I wanted to find the total duration of all the media in a keyword collection, so I hit 'command+A' to select all. Only, the input focus wasn't in the Event, it was in the Event Library list.
As I type, FCPX is dutifully trying to load every clip from every Event from every drive. I have several drives connected, dozens of projects, and thousands – many thousands – of clips.
...and of course I can't interrupt it.
So that's lunch, then.