That's an old discussion that I organised in another thread already. In Belgium, you can NOT fly a Belgian-reg airplanes with FAA PPL. I know it should be possible according to ICAO. Bit it's against the law in Belgium, I have it in written from Belgian CAA. In Holland and France as well. Only UK does recognize FAA PPL as equel. See this topic:
http://www.pprune.org/forums/showthread.php?t=262649
That's just the way it is. No use re-opening that discussion...