IMessageSink mscorlib problem

Hi together, i get following error in my project an try to solve it since yesterday.

Maybe someone got an idea?

The reference to type "IMessageSink" was reportedly declared in "mscorlib", but could not be found.

Error on following Lines:

direction1 = workPart.Directions.CreateDirection(sketch1, NXOpen.Sense.Forward, NXOpen.SmartObject.UpdateOption.WithinModeling);

curves1[0] = line2;
curves1[1] = line1;
curves1[2] = line4;
curves1[3] = line3;

I've not seen that particular message before, but "mscorlib" is part of the .net framework classes. I'd suggest checking that for whatever version of NX you are using, the proper version of the .net framework is installed (and updated).