I am only having the blank lot issue with some of the 'in game' buildings. I have downloaded quite a few lots/dats lately so I dont know where to begin looking. The buildings that are not working are the 1x1 Petroleum tank and the 3x3 Maxis theatre. I am not sure of the exact names. I figure one of the industrial and commercial dats I dloaded lately must have caused this as it occured only recently.