Sorry for the double blog, but i really have to just get this off my chest so to speak. I was thinking about forrest gump who said "It happens" when i wrote the title to this, but basically I've enountered this quite a bit lately:
"We're changing too much, when things settle down, then we'll do something"
I'm sorry, but... what? This is agile, change happens, that's the whole 'cool' thing about it. We can handle change!
Can't we?
Not when the rug is pulled out from under us we can't.
When you say that you're going to do Scrum, you're saying this to the team.
"Hey, we're giving you this prioritized list of work, you choose how much you can do in 30 days, you go and do it, call us if you need anything, but when you come back in 30 days we expect that stuff to be done just as we described it to you today"
Anyhow the point is, a team needs SOMETHING that is constant:
give them a constant iteration length
give them a sprint planning, scrum meeting, and retrospective that they can count on.
give them a product owner that can answer their questions within 1 day (or less)
give them uninterrupted time (iteration length) to work.
hold them accountable at the end of the sprints. (as a team, not as individuals)
When something increases in time, the team needs to know that they have to remove something else from the backlog, or put that item on the backlog.
In fact, here's something hypothetical i'd like to show you.

if this is a burndown, what do you suppose probably happened here...
still thinking? <pause here until you got an idea>
Here's what probably happened: The team didn't take enough work, and they decided to start doing more and more of a certain backlog item with the customer. Basically scope was sneaking in on them because they felt like they had time to spare. This is where the scrum master should have probably stepped in and said "hey what's going on here?"