If you've downloaded OS X 10.9 Mavericks, be sure to run Software Update via the Mac App Store after you've installed it. It seems Apple wasn't able to include a version of iTunes that was fully compatible with the latest OS X, so they've released a supplemental iTunes update as well.
iTunes 11.1.2 now offers official Mavericks support, according to its release notes, as well as offering support for Arabic and Hebrew, and features additional bug fixes. iTunes 11.1.2 can be downloaded here or via Software Update.Apple releases iTunes 11.1.2 with OS X Maverick
