Any custom steps that refer to their base classes after the step is complete (e.g. in evaluateCommand) can break if a reconfig happens while the step is running. The fix is to store a reference to the step's base class in the __init__ method, and then to use that reference in subsequent methods. There are several steps where this isn't happening. L10nVerifyMetaDiff for example.
Bug to be dealt with at due time.
Mass move of bugs from Release Engineering:Future -> Release Engineering. See http://coop.deadsquid.com/2010/02/kiss-the-future-goodbye/ for more details.
Lukas, I was touching so many steps in bug 505512 that I ended up doing this, so I'm going to steal this from you.