I've been able to get mine working. The problem was the com port driver. The one that comes with windows didn't seem to work. Downloaded the vcp driver from ftdiby toasthall - Sanguino(lolu)
I am having the same issue with my Melzi board. I uploaded the bootloader and still the same issue. I might try an older version of the Arduino IDE Daleby toasthall - Sanguino(lolu)