Read the whole post... embarrassing. But basically this is the solution:
- wire the programmer and the Mega (or in this case the Freeduino Epic) like this:
Programmer Mega
D10 (SS) Reset
D11 (MOSI) D51
D12 (MISO) D50
D13 (SCK) D52
Gnd Gnd
+5V +5V- download the sketch from here:
http://gammon.com.au/Arduino/Atmega_Board_Programmer.zip and upload it to the programmer Arduino
- set the Tools/Boards the target to Mega (1280 in my case)
- open the serial monitor, type 'g' and hit Enter
Taraaaaa! That's it! Special thanks to Nick Gammon for the excellent post and the sketch!