Uh oh, sounds like there’s some bugs being introduced into the gilded cage that Mac users seem to enjoy so much. Turns out that the new version of iTunes is deeply attached to Safari. This is causing problems for users of older versions of the browser, and also for users that have pre-release versions of Snow Leopard.
In most cases, it’s fairly easy to get around this, all you have to do is reinstall Safari and it’ll work. There have been some reported cases where that solution hasn’t worked, and for those unlucky people, there isn’t an answer yet. There’s also a problem with the Genius Mixes. Safari is again at fault, it’s causing the Genius Mix feature not to show up in the iTunes listings. In that situation, the best solution is to go to the iTunes store menu, and update Genius. If it’s still broken, you’ll have to turn off Genius and then turn it on again. Apple seems to have created quite a mess with their lastest software release.