I'm not sure what's causing your Mac to hang up while rendering. Does the scene have large amounts of volumetric materials or volumetric world active? I find that tends to seriously slow down rendering time - I'm on a PC. It's possible to convert an object to a light source. I'm guessing you still want the cylinder in place as well as the light? Duplicate the object to be converted. Then, in Create (IIRC), move the pointer up to the top where the little arrow is. There, you should see a little row of icons which mirror the main shapes in create. Simply click on the light type you want with one of the cylinder duplicates selected and Bryce will convert the object into a light. You'll probably need to remove textures and gels from the light by "E"diting it. Hope this helps Paul