The changes are irreversible, so if you plan on playing back your MP3s with WMP12, make sure to back up your music library. Microsoft is currently hard at work readying a Quick Fix Engineering (QFE) patch that will be distributed by Windows Update. A Microsoft employee has confirmed the bug and said that the company will be addressing the problem in the beta program. While many builds have leaked so far, most beta testers still haven't received builds to test.
Full Story: http://arstechnica.com/journals/microsoft.ars/2009/01/05/warning-wmp12-beta-could-corrupt-your-mp3s

