Clearing the Caches:
If programs appear to be retaining old or incorrect data (Finder icons are wrong, System Preferences has wrong or duplicate items) or, again, if applications are just generally behaving strangely, you should delete your caches. Is is completely safe to remove the files stored in cache because, as the name implies, they are only cached copies of data that are stored for quicker access. They will be regenerated as needed.
You should close all running programs before clearing the caches. This will minimize the chance of problems arising if an application is expecting and tries to access the cache. You should then restart your computer (or at least log out and log back in) after deleting the caches so the Finder and other system services will be refreshed.
To clear the caches, delete the folder named "Caches" in your home's Library folder. If you are the administrator of your Mac, also delete the "Caches" folder from the top-level Library folder.