I just got a new Arduino Leonardo board yesterday and it worked flawlessly after i first plugged it in to my notebook. I also uploaded some programs and tested with some devices on the breadboard. No sign of error was found at that time.
But after i unplugged it and moved to another notebook this morning. The Arduino Leonardo entry does appear in the device manager for a while between the L led has been blinking then the entry became hidden from the list. Pushing the reset button gives the same result as re-plugging the cable.
I thought it was the voltage problem. So, i put the 9v external power to the board and nothing changed.
After forcing the device manager to show all items, I've found my device with the lighter color of icon (as in the attached picture). By entering the properties menu, it said "Currently, this hardware device is not connected to the computer. (Code 45)" while my cable is already connected and the green led is turned on steadily.
Also found a guy that's facing the same problem with me here http://forum.freetronics.com/viewtopic.php?f=27&t=1360
. Surely no answer for him yet :/
Any suggestion ?