Hi!I had this problem too, looks like it is a common problem not limited to the retrode.Following the instructions there brought me fúrther, problem is described there: http://blogs.msdn.com/b/usbcoreblog/archive/2013/11/26/why-does-my-usb-device-work-on-windows-8-0-but-fail-on-windows-8-1-with-code-43.aspx, go straight to the Workaround! You can search for the following sentence: "To apply the workaround for a specific device, add a REG_DWORD value named SkipBOSDescriptorQuery that"(Though I am not done with flashing yet, at least no usb error and usb connection can be opened.)edit: Flashing is now working.