Passing any kind of data in HTTP headers can be a tricky business - especially for Flash based technologies.

What exactly am I talking about? Take a quick look at this link for starters...

ActionScript error when an HTTP send action contains certain headers (Flash Player)

If your reaction is 'no big' to this Technote... you can go get a cup of warm milk and get ready for an un-interrupted nights sleep. If you just nearly popped a blood vessel - I have a moral for you and a suggestion.

Moral of the story? Base application architectural decisions on rock solid paths. The more common (and well traveled) the path is... the more hesitant solution providers will be to release changes that will result in 'bustage.' See that roll-back on 9.0.124???

The suggestion? Well... there are a few. It is important to review Adobe Technotes from time to time and better yet make a habit of testing/re-testing all your software as soon as early release drops are available. Finally, encourage members of your development team to subscribe to an email list, blog or other news source that Adobe actively participates in. Last but not least - budget the time it takes to do these tasks effectively into your development cycle(s).