Tried again. The installer worked its way through the Fences\Images folder for about ten minutes, updating a .png file every 4 seconds or so.
It got stuck for several minutes on PagerBulletS@100.png
Finally, after 15 minutes, I got a popup saying:
Notice
The following file is in use and can not be updated:
Fences\Layouts\Bottom.fencelayout
Close apps and click Retry or Cancel to install on reboot.
I clicked cancel but then the next file's popup said the same thing.
This repeated for a while until I finally told the entire install to cancel, at which point it asked if I was sure and to press cancel to install on reboot. I clicked cancel but the popup kept happening so I had to kill the install process.
Guys... who wrote this installer? Wow.