Hi everyone!
I do have the same problem! It seems I can't upload anything on my arduino UNO R2. I'm still able to upload sketches using an USBtiny, but no communication between the computer and the board when using the usb connection.
I got an "avrdude: stk500_getsync(): not in sync: resp=0x00" error when trying.
Although I followed the advices given here, I'm still stuck.
My board doesn't pass the loopback test.
The other problem is, I can't seem to be able to get the atmega 8u2 in DFU mode. It does nothing when I try to connect reset and GND from the pin on its side.
Well, to be honest, I think it did something the first time. I had a new device in the device manager (I'm using Win 7 64 bits here).
But the only driver accepted was the arduino one for the Uno board. It didn't accept the flip driver...
Any hints on what should I do now?
Thanks!