System Preferences icons lost/gone all the same 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.
EDIT : My link concern an older version of Mac OS so you will not find all the files.
I updated my answer to match with my version of Mac OS (10.7.3).

It's seems that this person had the same problem and found a solution on this site.
Try the following and let us know what happens : 


  Quit System Preferences if it's running and trash the following files (make a copy of these files on your desktop for backup purpose) :
  
  /Users/yourusername/Library/Preferences/com.apple.systempreferences.plist
  /Users/yourusername/Library/Caches/com.apple.preferencepanes.cache
  
  Then log out/in or restart and check System Preferences for proper
  functionality.


You can access your library by pressing the CMD key when clicking on the Go menu of the Finder.

And about the reason of that change it can be possible that one of the setting file of the system preference pane has been corrupted. That's why you can try to trash settings file and see if the problem is gone.

Hope this helps !