Xbox 360 HD DVD Firmware Upgrade

Due to problems with the drive not playing certain titles, including "Children of Men" and the calibration tool from "Digital Video Essentials" Microsoft have released a firmware update to address the issue. Also, due to the drives inability to support the Dolby TrueHD audio format, the update will also convert (according to the Japanese source) the TrueHD stream to 1.5 Mbps DTS.

Source: AVWatch