On Natty Narwhal, I dragged System Center to the launcher. Instead of an icon, I get a blank square on the launcher. Clicking on it does launch the system center, though. This issue does not happen with other apps I pinned to the launcher.
closed as too localized by jrg♦, Marco Ceppi♦ Dec 27 '11 at 21:49
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If I got you right, this happened after upgrade? So try to remove those icons from launcher, and drag them again into the launcher e.g. from /usr/share/applications. That worked for me. Please also check this question Icons missing from launcher, system settings, folders and its answer.