It appears that the final specification for the Advanced Access Content System (AACS) has yet been postponed a little longer. This spec is used on both HD-DVD and Blu-ray Discs.
Why is this spec holding everything up? Well, because it deals with a “security specification” that both devices share to guard against piracy.
Another interesting note is that this “sticking point only applies to the Blu-ray specific BD+ anti piracy measure.” BD+ is a state of the art “encryption scheme” that makes it possible to alter it “midstream.” This if it is “cracked” the scheme can be altered so that it’s prevented from happening again.
The AACS spec tries to handle this complication but "Blu-ray's members believed that additional protection was necessary."
It is thought that this delay will push the arrival of these highly anticipated players back a month or more in the marketplace.