niadh:
When I launch the ide from a windows machine (which is the latest version) the internal led blinks correctly. I am stuck using the 21 revision of the software under linux because I am using a 64 bit os.
Which internal LED? There are 4 LEDs on the board, the one marked L is the pin 13 one. If that blinks pin13 works.
Have you remembered pinMode (pin, OUTPUT) in your investigations?