All my desktop icons via GNOME in FC12 are gone. When I first installed FC12, it's on the desktop, but now after more than one upgrades, the system's going crazy with no desktop icons. Thanks.

You can try deleting :
.gnome .gnome2 .gconf .gconfd .metacity

from your home directory.
Then log out and back in.

rm: cannot remove `.gnome: No such file or directory
rm: cannot remove `.gnome2: Is a directory
rm: cannot remove `.gconf: Is a directory
rm: cannot remove `.gconfd: Is a directory
rm: cannot remove `.metacity: No such file or directory

Update:
Just now it says only rm: cannot remove `.gnome2: Is a directory
Everything else says: No such file or directory

Tried your suggestion, but still no icons on desktop.

Have you got an entry in Applications > System Tools > Configuration Editor ?
If not you can
yum install gconf-editor

When that is done you can open that program and navigate through the tree to /apps/nautilus/preferences and check (or uncheck) the show desktop option. This will show (checked) or hide (unchecked) desktop icons.

I don't know if that's the problem, but it won't hurt to look.

Alternatively, try modifying your System > Preferences > Appearance > Themes

click Customise and select Icons tab and choose new icons style.
I don't know if that's the problem either, but it won't hurt to look.

What else have you tried ?

I don't know what happened but after reinstalling for the third time again now, everything's back to normal.

Thanks anyways.