@VHamptonthank you for the insight--I think you might be right--it must be some component I've added to the plan that is messing it up! I just started a new plan and drew a basic box with four walls, a door, and 2 windows and PRESTO, raytrace began! Now to figure out what is causing the issue in my other two plans.... (I have downloaded a few models from the SketchUp 3D warehouse so I'm guessing it might be one of those?)