Microsoft has identified a serious of issues with Windows Media Player and the Windows Media Center on Windows 7 Beta. This include corruption of MP3 files when editing their Metadata.
Download and install the update KB961367 from the following links or from Windows Update to resolve the problem:
The problems fixed with this update for Windows Media Player & Windows Media Center are as follows:
MP3 File corruption issue
Protected tuning sources, such as OCUR and ISDB, do not function correctly.
MHEG (iTV) in Europe does not function correctly.
Recording of a series may fail after some time if the system was upgraded from Windows Vista and the recording of that series was set up in Windows Vista.
Windows Vista DVR-MS recordings do not play back in Windows Media Center or in Windows Media Player.
Windows Media Center may become unstable when you perform recording operations.