If you ever encountered this exception and wondered what it means, here’s the answer: it doesn’t mean anything. This is the default message text of the InvalidOperationException. If an invalid operation exception contains this text, someone was too lazy to supply a real error message when throwing an exception and did just “throw new InvalidOperationException()”.
I wasted hours trying to figure out why the Sync Framework’s FileSyncProvider keeps complaining about the state of an object, which object’s state this is etc. only to find out that someone at Microsoft was loath to spend one minute to at least write a meaningful message. Hopefully, this post will save someone else’s time.