Panel not showing running programs' icons

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http://www.kubuntuforums.net – Take Firefox, for instance... there's no indication that it's running, so I click on the FF icon and FF starts, with a "Firefox <2>" as its identifier. Thunderbird starts a second instance, but with locked account settings (because the invisible first instance is using them, I presume). How to I get the running-program icons to show up again in the panel? They were there when I first installed Raring! I've been fooling with the panel, inserting a spacer etc, to try to get some of the items at the right (clipboard, volume, network, clock) while leaving some at the left (program- (HowTos)