Invalid Clicks are quite natural, but you should alway report it back to Google. https://www.google.com/adsense/support/bin/request.py?contact=invalid_clicks_contact
Yes, two days ago I detected invalid clicks activity on one of my sites, I promptly reported to Google and Google replied to me assuring me that they will look into it and that my account is not in danger. Moral of the story, always monitor your stats and report to Google if you find anything suspicious. Otherwise they will think you are an accomplice. - MENJ
Nice. I reported mine as I think I accidentally clicked today with this stupid wireless mouse that keeps running low on batteries