Thanks for posting this here, Nick. I was going to do it but was traveling for a while. I was the one who brought it to the attention of the Microsoft team, and honestly I'm astounded that this was not picked up earlier. It's a pretty serious flaw in my opinion. People need to know about it to avoid a lot of wasted effort like I and some others have encountered, until the fix is released. You can read the details on the MS Expression Media forum here:
Re-ordering Hierarchical Keywords jumbles image assignments: bugArlen