Looks like reflections from lights to the sides. This happens easier with cheaper zooms. Can also happen if you have a UV filter on. I had it happen on some moon photos I took, removed the filter and good to go. If it's side light a hood can help too.
If the images of the lights are positioned opposite the sources in the frame (if the source is at lower left, the image of it winds up at upper left in roughly the same position), what you have are ghost images. This seems *really* bad, and I have not had this issue with my 70-200/2.8 IS. Like others, even though you state "no filters" are you sure there wasn't a UV filter on the front of the lens? UV filters are notorious for this (and other) negative effects on image quality.
