Hi,
On the menu bar click on View and then choose details. Then after that try to rebuild your icons.
This is because this is a locked folder don't know why MS did it that way, but the icon was in use when you tried to rebuild the icon cache. If you have the default winxp folder icone with an "e" (internet explorer logo" in the details view, then there's a chance that it will work.
let me know if it work. This is an internet explorer folder. Maybe you should try to reinstall IE but don't reinstall it for now, I'll try to find another way. but as others told you, this is not a big deal.