I found two links to a Harduino and one is not using the same setup as a arduino and one is a homemade board that needs a USB to tll upload cable.
Com port can be a problem It happens if you plug in to a different port with the ide open more then if you have the arduino plugged in the USB at start. And some of the arduinos don't handle bootloader mode right you have to press there button to get it into boot mode and one of those is tricky. You watch the ide and as soon as it tells you it's none compiling you press the button.
I think I'm probably in your bad books already .. .. the H'arduino was a play on words because I couldn't get the damn thing to work ! It turned out to be a dodgy board with a 'once only' load syndrome .. .. as I said in an earlier post, it was last seen passing the ISS on a trajectory for Mars as a result of an encounter with my left boot !
I'm now working on a PIC based Tacho .. .. see if I can bugger that up too !
Could it be possible that the boot loader somehow got overwritten? An AVR programmer and reflashing the boot loader would fix that. SparkFun sells their pocket AVR programmer for $15.