Created attachment 84242 [details]
No selections are shown even after ticking the two checkboxes and selecting a folder

This bug has been described in detail at:

http://www.mail-archive.com/kubuntu-bugs@lists.ubuntu.com/msg42074.html

and at

https://bugs.launchpad.net/ubuntu/+source/kde-workspace/+bug/1253528

At the latter site, it was suggested that it was KDE bug rather than a K/Ubuntu bug.

I am not the original reporter of that bug but can confirm what the original bug reporter stated:

---Quote ---
Plasma forgets settings made in the settings dialog with the title
"Desktop Settings - Plasma Desktop Shell", accessed by right clicking on
the KDE desktop background and choosing "Default Desktop Settings".
--- Unquote ---

Attachments have been given by the original poster at the above sites. For completeness, I have attached the relevant screen *AFTER* the wallpaper slideshow settings have been saved.

Thank you.