seems like this is useful
" Windows 7 themes change your custom icons
Windows 7 has some spectacular new themes - there's a great selection at the Microsoft site - but installing them can have one annoying side-effect. If you've previously changed a system icon like Computer or the Recycle Bin then that could disappear, replaced by the equivalent icon from the theme pack.
To prevent this, right-click an empty part of the desktop, select Personalize > Change Desktop Icons, clear the "Allow themes to change desktop icons" box and click OK. Your icons will now be preserved, and the only way to change them will be manually, from the same Desktop Icons dialogue
"
also
clearing the icon cache seems the only solution
there are different methods I recommend you try them again
http://smallvoid.com/article/windows-icon-cache.htmland if not solved rebuild seems the only solution so back to square one

ps: once you have correct icons back up frequently in a different folder than desktop so you can delete all and restore again..