SOLVED!, well, not exactly...
When reinstalling Archicad 9, everything works perfectly...
When updating to build 2219, same problem again.
So finally, i repaired Archicad (to original build - v9), without installing the update.
I think there must be a conflict somewhere. I have no idea where it could be but the 2199 build does corrupt my DWG import/export add-on.
Thanks for the hint Matthew.