MEGA 1280 TROUBLESHOOTING

Hi Everyone!
I have installed Arduino MEGA 1280 on a PC with Windows 7, updated the corresponding drivers, and selecting the right card in Options -> Board, in this case, Arduino Mega 1280.
I run the first example by first compiling and then uploading the program into Arduino Card:
Before uploading the led on the board is blinking continuously, then after uploading, it stops blinking, and finally it gets back to the blinking status (the led on the board). I have checked that all connection on the board are connected properly.

This gets even worse, I have also an Arduino UNO Card connected to a Mac computer. Here, after uploading I am getting the following message

avrdude: stk500_recv(): programmer is not responding

I have tried to use also this card in my PC, but it is not working neither.

Any help in this matter will be highly appreciated.

Intarsia.

Hello

can you let me know the serial number of the Arduino Mega 1280?

m