First of all: I'm no electrician. Despite having read many books on the subject, I still can't differentiate between my watts and my amperes. So when I couldn't get my indicators to work properly I had to consult a friend (thanks Erik).
The problem was that when I had replaced my standard indicators, which used a 23 W light bulb, with my new mini indicators, which contain LEDs instead of bulbs, the current would "creep" (lay mans term) around the system and make all four indicators light up at once. A bit confusing for the people behind my bike. I had changed the indicator relay for one suited for LED indicators, so the blink frequency was correct, but the "Christmas tree" effect persisted.
It turns out that LED indicators use as little as 1 W and thus the current would go through them almost without noticing the LEDs (again: lay mans terms). So to make it work we had to install a couple of resistors to "fool" the system that the 23 w bulbs where still there. Two resistors from "Biltema" did the trick once they were installed together with the rear indicators. Just remember to install them "in parallel" with the indicators. Now everything works and its time to shrink hose the whole loom to make it reasonably waterproof. Not that I'm ever going to ride in rain, but still.