OK… so my Dragon just stopped working. Plug it in, the status LED just flashes amber and Windows (XP) does not detect it. Re-install the drivers – no, that isn’t it. (BTW, the instructions in the helpfile that comes with Atmel Studio 6 are wrong). Try another PC or using a motherboard USB socket rather than the hub – no, wrong again. Try a different USB cable – nope.
The answer, it seems is to use a USB hub but to do so with the hub’s separate power adapter. After that, I was able to dispense with the power adapter and the Dragon kept working, even after unplugging/re-connecting.
Wierd! There are a number of suggestions on the web that the Dragon draws a heavy current on startup, so I guess it got into “a bit of a state.”