There is something wrong either with your desktop or the x resources configuration. Assuming you didn't do anything the situation could have been from your windowing handler.
--Logout without saving the session.
--Press Ctl+Alt+F2 (or F3-6)
--Login as normal user in the shell and issue this:
~$ rm -f .ICE* && find ~/ -iname \*cache | xargs rm -fr
--Login as normal user. See if icons are restored.
Hope that helps.