Hi, I just encountered this problem today when trying to update my Pod HD500 to the latest firmware. I tried different USB ports, different USB cables, and several of the other suggestions, all to no avail.
I have many cables plugged into the back of my Pod HD500; midi, variax, headphones, left/right outputs, another guitar...
I thought I would unplug everything, other than the power and usb cable. Lo and behold, looks like one or more of these cables were causing problems, and after unplugging them, my flash update worked flawlessly.
Hopefully this will help others who may be having difficulty updating the firmware.
