cannot download itunes purchases

I get the following error when trying to download files from itunes store

itunes couldn't download your purchase
you dont have write access for your itunes media folder or a folder within it. Change permissions (in the finder) and then choose Store > Check for available downloads

I have been into my itunes folder and changed the permissions to deny access to anyone else other than administrator and made administrator read and write plus applied changes to all files/folders within the music folder in finder ( a thread on another site said that sometimes allowing access to other users can cause problems). This hasnt worked.

Any ideas from a mac genius? My son cannot download any of his birthday purchases and is getting desperate!!!

You have messed up the permissions for that folder by fooling around with it without understanding what you were doing.

The folder called "iTunes" in your home folder (I'm assuming you have the latest iTunes) should be: [your account] read and write; admin read only; everyone read only. The iTunes Music folder inside the iTunes folder should have the same permissions.

Good luck.

thanks chas

I did a bit more searching and found on the apple help a prompt to check the SD folder if multiple users have permissions to view the files. When I imported my old I tunes library from my old macbook it had duplicated the SD folder which probably exacerbated things. By deleting all the SD folders (which I found using finder) and restarting the Mac the error was corrected and I have spent a fortune down loading stuff on itunes since.