I get alot of them on my site, in fact most of my clicks seem to be like that but I dont care and gave up, if the clicks come then I am happy if they dont then never mind
The clicks could also be CPM advertisements that don't have for clicks. I have a few sites that are earning CPM for whatever reason (targetted or not?), and on those sites I do see clicks that earn $0.00. Nothing to be worried about as the CPM ads do pay fairly well over time.