I found that the move single message function is not working when trying to do a move within a pop-window (which I do often because I'm reading complete thread).  In FF at least  it took me to this result:

Sorry, but the information you are looking for is not available,
or perhaps you entered an invalid URL.

So, I tried doing a move message from a standard page and found it is not working there either.  FWIW, other similar functions all work fine--change thread and change thread partial work perfectly as I've used them many times since the code change.  I just rarely have to use a move message.