UNO unresponsive

Hey all, everything was working fine with my UNO R3 until last night. I don’t recall connecting something where it shouldn’t have been, but now I can’t get any response to the computer.

Basically the UNO no longer launches in Device Manager (I’m running WIN XP), I’m not seeing a COM assignment. The RESET button no longer seems to have any effect. It seems the program on there before the issues started is still running but honestly I’m not really going to be able to test for that as all that was running was a NEOpixel test at RGB value of 1 ( I was in the process of trying to speed up response from an optocoupler so it would work at PWM value of 1). I’ve tried connecting it to a different computer and I saw no connection there either.

After doing some research I came across talk of re-flashing the firmware on the ATmega16u2 but I cannot get the UNO to go in to DFU mode (crossing the pins closest to the USB port has no effect).

So basically right now I’m stuck until I hear back from the place I bought it about a replacement unit. In the meantime has anyone else had this issue and fixed it? Is there any way I can check to see if I have actually burned out the 328? As I said I’m fairly certain I didn’t cross a voltage to somewhere it shouldn’t have been.

Hi !
I post here because it seems that I have the exact same problem with my arduino R3 SMD board. I have been using it for now one week without having any trouble but since few days the board does not respond anymore, before posting here, I tried to read as many forums and topics as I could but each time it is said to install the drivers for the arduino device, but since it does not appear in the device manager, doing such a thing is impossible. Actually, pluging the board to the computer seems to not have any effect while the power LED on the board switches on and the yellow one stays enlightened. I do hope the board is not out of order. . .
Then, while we seem to be two persons having the Same kind of trouble, I wish somebody could help us out making the board work again.
Thank you in advance !