Using a Japanese version of WinDVD HD, Doom9 forum-goers (with an extremely helpful tip from Muslix64) have uncovered a way to determine the title and volume unique keys of any AACS encoded HD-DVD. While this is not permanent, it will allow users to decrypt any movies that are currently in release.
The trick is based around the "known-plaintext attack" that allows users to find the volume and title keys in predictable places in memory every time. Using these keys and BackupHDDVD, users can decrypt any AACS-encoded HD-DVD.
There will be a fix for this released by media companies. The current DRM scheme will allow them to disallow new discs to be decrypted by players it deems untrustworthy, so with the next set of releases there is no doubt that this specific version of WinDVD will be put on the playback blacklist.
Update: There appears to be a similar weakness in the recently released PowerDVD 7.1