I'm using the awesome wm and awsetbg to draw the background. Suddenly, for a mysterious reason, it doesn't work (awsetbg /some/file.jpg), and when I try to get it to use a random directory (awsetbg -r /path/to/pics/dir) it says "invalid random wallpaper directory." Why is that, and how can I fix it? The directory doesn't contain anything but image files.

Update: I tried both awsetbg -r ~/Pictures and awsetbg -r /usr/share/backgrounds, but neither work.