- terrible typo was making the multiplication to run in an infinite loop.
- Any matrix * vector multiplication would crash Blender.
eg
####
import Mathutils
from Mathutils import *
vec_ray = Vector(0.0, 0.0, 1.0)
tilt_mat = RotationMatrix(0.0, 3, "y")
vec_ray = tilt_mat * vec_ray
####