Kernel crashing on this line..why?

I have a kernel that is working with a cuComplex array.

  Shift = make_cuComplex(__cosf(6.283185307179586476925286766559f * factor), -__sinf(6.283185307179586476925286766559f * factor));
 d_data[i*cols +j] = cuCmulf(d_data[i*cols+j],Shift);

Those are the relevant two lines,w here Shift is a cuComplex, and d_data is a rows*cols matrix of cuComplex.

This crashes with an unspecified error, however, replacing the last line with any of the following lines all work:
d_data[i*cols +j] = cuCmulf(d_data[i*cols+j],d_data[i*cols+j]);
d_data[i*cols +j] = make_cuComplex(0.0,0.0);
float test = cuCabsf(Shift);

so my probelem seems to only happen when i try to use my data and that Shift value.

Any ideas whats going on here?