I have Mac mini (mid 2010) server running Mac OS X Server Lion 10.7.3 (11D50b)
At some unspecified point in time (which could have coincided with the installation of Logitech Media Server to serve a SqueezeBox in the next room, but I can't prove that), all the icons in the System Preferences turned into the default icon of System Preferences itself.
Besides the visual change, everything else is working as expected.
Now, the primary question is - how do I get the icons back? Secondary question is, how this could have happened and what could be done to prevent that.