avrdude: stk500v2_ReceiveMessage(): timeout

I have a Geeetech GT2560 Rev A board for controlling a RepRap 3d printer. I understand that's basically an integrated Arduino Mega 2560 plus RAMPs 1.4 adapter shield. The GT2560 is running, and it sends text to my IDE at 250,000 bps. I want to upload revised firmware to it & am having problems. I made a simple hello world sketch that also toggles the on board LED (pin13). This loads quite happily into a real Arduino. When I try loading same sketch into GT2560, after compiling it announces that it's uploading, but all goes quiet for about 50 seconds, then sends a succession of ReceiveMessages as shown on title line. This is the output:-

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
An error occurred while uploading the sketch

Then it stops. The original firmware still runs. I have tried hitting Reset at start of upload, but can't figure out how to get over this.

I have removed this board from all connections & had it powered from USB cable to IDE computer.

Has anyone seen this? Any ideas if I am doing something wrong? Is GT2560 faulty? Any recovery strategy?