Apple may be aware of the issue. This Discussions thread discusses the issue and RoyB suggests re-downloading and re-installing iTunes 9.2.1(5)you may have 9.2.1(4)as a solution. (Thanks Tom R.)
Update: I forgot to mention that Software Update will not report v9.2.1(5) as a newer version if you have 9.2.1(4). You must download iTunes from this page at Apple and install it from the disk image.