On a related note, Microsoft confirmed that it is also pushing the mainstream launch of Office 2007 to next year. The reason is that Microsoft wants to launch Office and Vista in tandem.
So the word of the week for Microsoft was DELAY. But what if the problems are so difficult to solve that they need another year? They're working for Windows Longorn since 2003, that's 3 years ago, and 60% of the code they wrote needs to be rewritten. I think this needs almost 2 years, so the best thing to do is set a new deadline: December 2007.