Weird behaviour of Statistics-related panels on the Administration page

Steps to reproduce:

1. Hover over Home and click on "Administer Wiki"
2. Click on "Panel Wizard"
3. Drag and drop some Statistics panels from the panel list to the sides; for ex. you can use Current Month Activity, Most Viewed Pages, Most Referred Pages, Current Year Activity etc.
4. Click "Save The New Layout"
5. Reload the page
6. Try to drag and drop the previously added panels from the sides to the panel list; you'll notice you're unable to remove them (before.png)
7. Click "Save The New Layout" even if there's no visible change
8. Reload the page (after.png); as you can see from the image the other 2 panels have been removed.

If you try to remove the Statistics panels again (steps 6 & 7) they'll be removed.

Reproduces on both Firefox & Chrome.