I have some problems with my arduino uno r3. It worked without problems.
After using it with an ethernet shield the arduino L-Led is blinking constantly without uploading a new sketch. Also it's not possible to upload any sketches to it. In Device-Manager on Windows it is only recognized as unknow device and when I force a Driver-Update with the Uno Driver it says error-code 10 (Can't start device).
After that I tryed to update the firmware with Flip but it says that it can't write to usb.