iTunes: unable to authorize and unable to download media

"I changed the group owner to be ""admin"" instead of ""wheel"".

Despite the fact that the Apple KB says that the group owner should be 'wheel'."

"I had a similar problem.

First check the permissions for the iTunes application:

ls -l /Applications/ | grep 'iTunes'

You will find iTunes owner is root and is in the wheel group. Check /Users/Shared - it will have the same permission.

I found I had deleted /Users/Shared when I removed StarCraft 2.

Entering the following commands fixed this and iTunes worked again:

sudo chown -R myusername:staff iTunes.app
sudo mkdir /Users/Shared
sudo chown -R myusername:staff /Users/Shared"

"I had a similar problem with the same error message. I found this:

http://forums.cnet.com/7723-21569_102-402712.html

In summary, run the following command and it will be fixed:

sudo rm -rf /Users/Shared/SC Info"