Mendel Ramps 1.4 Arduino - no connection (no replies)

I completed the assembly and wiring of my Prusa Mendel i2.

Having installed all the software on my PC, I connected the Arduino USB cable to the PC.

No lights were shown on the Arduino and the PC didn't detect any new hardware.

I have disconnected all the wiring from the RAMPs so it is now a bare board.

When connecting the USB the Arduino LEDs now light up, the green LED on the RAMPs board flashes and the PC has detected the hardware. I've managed to install the Arduino driver and a COM port has been assigned.

However, pronterface is unable to connect to the printer. I have checked and double checked all the settings. The command line shows, "Connecting ..... Can't read from printer (disconnected?)."

Is it possible that the hardware fault when wired up (I assume there is a short) hosed the firmware? Should I re-flash the firmware? Any other suggestions / diagnostics appreciated.

Thanks.

James.