Thanks, balasar.
But this has nothing to do with Muton's Tool I suppose, but with differences between Windows & Linux.
I think the POINT in light.c conflicts with the typedef in windef.h & now UFO:AI is not Windows MinGW compatible anymore
I will write open a bug tracker item on sourceforge & assign this to arisian, I am sure this is a minor problem which will be repaired soon.
Thanks again for helping me find out that I am not alone with this bug