LEGO Mindstorms NXT - bossa driver prevents firmware upgrade
Read the RobotC NXT Forum thread Firmware Update &amp; Arduino IDE Issues (Renamed). The only post that count is the 31th post. Simply go to the Device Manager with the brick connected, choose the Bossa Device, choose property, pilot update and replace the Bossa device by the Lego Mindstorm device.

Here are the explicit instructions from that post:


Complete a Hard Reset on the NXT Brick


Push and Hold Silver Button on Back of Brick for at least 10 Seconds
You Should Hear a Clicking Sound

Plug the NXT Brick into the Computer via USB Cable
Click on the Windows Start Button
Right Click on Computer
Choose Manage
Expand the Ports
Right Click on the “BOSSA” Port
Choose Update Driver Software
Choose Manual Selection
Click “Choose from List Provided”
Select the Lego Option
Open RobotC
Click Robot and Download Firmware