I would try a different case. Some times there are hardware incompatibilities between the IDE to USB interface in the external case and the USB controller on your computer. It could also be a driver issue. I would check to see if there are updated drivers for you computer. You should check the computer makers website. You might find newer USB drivers. And sometimes Windows will install a Microsoft generic driver for the hardware when there are better drivers available for download from the manufacturer.
In any case, it looks like a Windows problem and not a Winuae or Amiga problem.