so i have a probleme with my arduino uno r3 (new) . yesterday it was working perfectly but this morning i wanted to load a new programme on my arduino !!!!! my uno is not detected (no sound when i plug it in ) nothing happens
i uninstalled the driver and reinstalled it but no changes , i changed the usb port same results i also changed my usb cable but nothing is happening ...... i'm running a win 8 .1 x64 . i tested the arduino on another computer (win 7 x64 ) but it didnt work .
i have the green led (on) works .
when i plug my project and try using the programe wich i uploded the first day it warks perfectly .
i need help please
sorry for the bad english
Bad cable perhaps? It's just wire, they do fail.
i tested another cable (my printer cable ) but didnt work .
ill by another cable and test it.
but the cables works on any other device......
any other suggestions ?
Souds like the on board serial converter (Atmega16U2) is dead or damaged, could it have been damaged in your projects?
i dont know if it's damaged but as i told u i have a probleme only when i'm plugin my arduino to the computer to programe it .
the programe i used is runing with no probleme even now .......
i readed some article on bootloader (flashing or updating .....) . can this processe help in my probleme ?
sorry Mr CrossRoads i have tested a new cable but i have the same results my arduino not detected =( =(
need help please 
Hi, same problem here on Windows 7, but I managad to fix it, which is cool because now I dont need to buy a new Arduino : 
Follow the steps as described here:
https://www.virtuabotix.com/how-to-cure-sudden-uno-death-syndrome/
Basically you have to install the FLIP Software from Atmel, put your Arduino R3 Uno into DFU mode by shorting the 2 pins near the USB plug for about 1 sec, update the device driver and than flash the Atmel16u2 with the correct firmware hex file ( I used this file: C:\Program Files (x86)\Arduino\hardware\arduino\firmwares\atmegaxxu2\arduino-usbserial\Arduino-usbserial-atmega16u2-Uno-Rev3.hex), and finally deactivate the DFU mode.
thx for your "REPLY" i have a lkitle probleme my arduino uno r3 wont change to dfu mode i have shorted the resete end the gnd like they said in the tuto but my arduino didnt pass to the dfu mode no blinking nothing alwys the on led works when i reset the arduino i have the l led blinks then turns of need any idea how to put my arduino to dfu mode please ????