I think I had the exact same issue. ADB works perfectly fine, but while the phone is in fastboot mode, it shows up in Windows Device Manager as "Android" without a driver. I had to manually "force" install the driver to fix this:
1. right click -...
- Android 4.3
- Smart 3G
- Camera in 4.3
- Navbar extra settings
- Vibrate on Answer
Now I can't choose them T-T
same my problem http://forum.xda-developers.com/showthread.php?t=1460152
try reboot phone and transfer again
can transfer file from PC to GNexus but can't transfer from Gnexus to PC.
How to transfer ?