If you have an Xbox 360 HD DVD player, you'll be prompted for an auto update the next time you watch an HD DVD movie (and your are signed into Xbox Live.)
This update includes:
- Compatibility improvements with certain titles
- Additional support for network features
I suppose it can't hurt to give people better compatibility so that their HD DVD drive works with all the dirt cheap HD DVD movies that have started to become available!
Link: Major Nelsons Blog