Dxw00d, DuaneB,
Thank you. Instant success.
@DuaneB, thank you for your blog post. Very useful information. I love the fact that you only mentioned the common ground issue..euhm 3 times.......in bold.
If only I would have actually accepted the fact that I, as a beginner, could have made a beginner mistake in a 3 wire setup instead of spending hours searching on google on the assumption that it must be a very exotic servo I have, with a very special need for a very special protocol that I don't understand yet... yeah, that must be it... It can't be because I made a connection error..it's only 3 wires..... 
Well, at least I had the "external power supply for your servo" thing right. 
Thank you for helping me out.
Edward