Lights definatly seem to make a BIG differnce! When I did a Halloween render with 7 charaters and *** load of props it rendered in only about 5 or 7 min.....but a recent Christmas pic with only 7..oops 8 (counting the sleigh) charaters BUT with Lots of snow, lights but only a couple props = Would NOT Render at All..... I ended chopping it into Three separate scenes and then rendering and reassembling in PhotoShop. Yup, gotta be those lights and shadows....