You could also simply create a "screen" on the same layer as your furniture. Simply draw a rectangle the full extents of the drawing, with no bounding edge and a transparent fill in white. Arrange your furniture within the layer to back. Set the entire layer to be below your symbols.

Wow that's odd. It doesn't work like that on mine, so it isn't a typical behavior. I would guess this might be a windows malfunction? Or maybe a problem with the multiple monitors? I'll dig around and see if I can find anything on it.

SightSpace