There also seems to be an issue with broken cookies (seeing that iTunes Music Store is now using the WebKit), when you'd get an error while trying to Update or Turn On Genius.

To fix the problem:

1) Close iTunes.
2) Launch Safari and go to its Preferences => Security and click "Show cookies" button
3) Enter "apple.com" in the search field
4) Select all entries for apple.com in the list and click "Remove"

Now restart your iTunes and Turn On Genius - it should work fine now.

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I was pretty upset when I've found that when you are listening to a Genius Mix you can't change rating or other info of a song that is currently playing. Even using external controllers. Apparently this info is red-only when accessed in a mix. You can even open an info window (cmd+i), but you can't change anything there. So sad.

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http://support.apple.com/kb/HT3843

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Neither of these fixes worked.

I had to "Turn off Genius", which took a while to delete the genius database.

Then turn it back on, and go through the EULA, etc.

Now it works.

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