The strange behaviour of the unit, with the led's rapidly flashing, came from starving the board.
When I ordered the kit, the power supplies were out of stock, otherwise I would have included this in my order. So the first powersypply I used is a multiple output unit for guitar effects pedals, this thing came of a pedalboard and now lives on my workbench. I made sure the voltage and the polarity were correct but I didn't look at the mA rating. The leds came on so I assumed it was OK , it's rated at 600mA but lt is limited at max 120mA per output. So as soon as the software was loaded and the processor started up, the powersupply was insufficient, and starving the board caused this erratic behaviour.
I started it up afterwards multiple times with the 600mA rated single output powersupply and it works every time. Maybe this can be helpfull to others who run into trouble with the powersypply.