You might already have your answer and be well on your way. I came to SevenForums to see if anyone else had this resolved. Google turned up a lot of people like you and I who were frustrated by this message.
Although this is very much UNlike me, I took the advise of the MSDN and .... just waited. In my case I have a fast machine, but with a 2TB drive it took nearly 24hours to finally "work itself out". I was sitting here (on my ThinkPad) watching the numbers go by, and looking to see if I should just pull the plug (I'm not the most patient being), and 'whoosh' - it finally skidded to a stop - gave the customary 'end' message telling me what a good job it did.
So, my advice to anyone else who experiences this, is "let it run". Eventually it will (probably) come to a conclusion. Hopefully, your results will be good like mine.