I just got this notification in my Windows 7 (beta) System Notification Area:
Windows Update
Windows 7 Beta gets update to fix MP3 bug
There was a bug in the Windows 7 Beta that causes some MP3 file corruption issues. A few days ago a hotfix was released for MSDN subscribers (who also got the beta 2 days before the general public), and now the update is available on Windows Update. Happy days! (Related: Windows Update received an update in Windows 7.)