first i was actually using an Olimexino-328 (should have the same characteristics as an Arduino Duemilanove).
Now i tried the same code and setup on an UNO and it works.
Therefore i have now started a topic in their forum.
6v6gt:
What happens when you make a momentary connection between pin D2 and Vcc (+5v or +3.3v) with A0 pulled low ? Does the LED function for 1 second ?
it already does when unplugging it from low/ground (on both boards).
so it seems like it should basically work easily if it gets triggered already with no current flowing? 