Recuperating panel icons

[gilpel at altern.org]

As I explained here:

https://www.redhat.com/archives/fedora-list/2009-August/msg02753.html

a sleuth of icons have disappered from my top panel, but it seems the
problem is only with the icons: the applications still work.

For instance, I recently received a message at the bottom of the screen
saying updates were available. I clicked "install" and everything
apparently installed correctly. The problem is I don't have the update
icon in the panel and I can't check which updates are available before
they install.

Same for Klipper. If I press CTRL + ALT + V, the content appears, but
there's no icon to do so. Same for the new CUPS icon thaT checks for the
printer, and so on.

Of course, all icons have disappeared from the "Add to panel" menu.

Anybody knows of some way to reinstall the icons?