I have tried:
All It did was change my startorb back to a windows logo, and change the windows live messenger icon back to a different windows icon. Screenshot below:
Before clearing cache:
As you can see it changed my startorb back, and changed the icon for Windows Live Messenger. I have no idea what's causing this, but so far it seems to only be those programs. They appear fine in my dock, and on my desktop. But they do not work on my taskbar, or in my startmenu.