I have just seen a similar problem. Mine was a result of adding a file to the 'wishlist' after a zero search completed. In the download screen the filename was listed with the last character being an '*' (that is the last character before the '.mp3'), a file size was shown, the progress listed 100% and then the message 'Unable to move to library'. I verified that I don't have the file anywhere else on my drives, and when I chose 'clear inactive', it cleared and the next time I searched for the same file and added it to my wishlist it is doing the 'requery sent...' message as I would expect.
strange....