I was having the same problem.  I found the trick was to uninstall ALL the Line 6 Monkey stuff and drivers and then just download the driver direct.  It really frustrated me as I have a UX1 I was looking to sell and just wanted to double check it was in working order.  It was so bad it jammed the boot up of my MAC.  Just another reason I don't like Line 6 gear, it's always a little questionable about how well the stuff  will work.