I'm trying to adjust the scale and height of some objects, but the 'S' and 'Z' hotkeys aren't working. Did accidentally press something, or is the Creation Kit broken?

This may sound silly, but perhaps try restarting the CK? As far as I know, there's no key to disable the various move/scale hotkeys.

I did try restarting it. No luck.

EDIT: Okay, now it's working. Apparently whether or not it works is random.