Apple has updated its iTunes software to 10.5.2, with unspecified fixes for problems with iTunes Match.
Apple's brief description reads "iTunes 10.5.2 includes several improvements for iTunes Match and fixes an audio distortion problem when playing or importing certain CDs."
iTunes Match is Apple's $25-a-year service that stores your iTunes library in the cloud, matching the tracks in your library with those in Apple's 20-million-song catalog--meaning you don't have to upload them yourself--and letting you upload the ones it can't match (for a total of 25,000 tracks not purchased from the iTunes Store). It is currently available for US customers only.
You can download iTunes 10.5.2 directly from Apple's iTunes download page. At the time this story was posted, the software wasn't showing up in Software Update, and the Apple support page for the update was still showing iTunes 10.5.1.
iTunes 10.5 requires OS X 10.5 or later, and is also available for Windows XP (SP2 or later), Vista, and 7. The update is 102MB for Mac, 66.13MB for 32-bit Windows, and 68.01MB for 64-bit Windows.