I posted the random wallpaper script a couple of months ago, and some time after that I upgraded my system from Hardy to Intrepid, and found out the script wasn’t working.
Since it was not something important to me, it took me a while to start searching for a solution.
The problem is not a bug, it’s a change made to gconf.
Fortunately, someone was able to find a workaround to those changes. It only involves creating a shell script, setting it to start every time you log in (it will create a file called .Xdbus in your home path), and then you modify your crontable so that the .Xdbus file is called before your script.
Once you log back in, you should see the wallpaper being changed again! :D