My USB IDE enclosure has always worked without problem. Now suddenly, for no reason whatsoever that I can fathom, it works with some drives, but not with others. At first I suspected a drive failure, but when I plug it directly into the IDE connector on my test computer, it works fine. In the USB enclosure I can hear the head ticking as it seeks, but the drive doesn't read and it never registers. So far this has happened with two drives that always worked without problem before. A third drive still works normally. Can anyone suggest what is going on here? Much thanks for any help.