It would certainly explain a lot but no. I do like to have my textures sharp but not that sharp. The Carrara file is 19 megs. I understood that cckens would have liked to have both the C-file and the tiff-file so that he could test if the problem occurred also on PC. So, I tried to make the C-file's size a bit smaller by exporting just the object that has the errors. I closed the original file and opened the file with the exported object and rendered. The flaws were gone, even with the original tiff-file. Of course I can send anyone the original tiff-file but it is probably no use. The problem derives either from the C-file's size or something else that is in the file for also the curtains and the walls have been filled with similar errors.