The machine account %1 already existed on %2. This maybe the previous machine account whose deletion has not yet replicated ...

The machine account %1 already existed on %2.  This maybe the previous machine
account whose deletion has not yet replicated to %2.  If this is the case, you 
may need to run this tool again once the deletion has been propogated everywhere.
You will know this is the case if the following demotion fails.