This was a problem I saw happen if people were clicking on ads too often. The ads would not show up on a particular ip address but I would call someone else and they would see them.
I have a client who nearly got banned from Adwords and he still has his account BUT whenever he goes to a page with Google Adwords on it, his browser crashes... BUT when the Google Adwords were removed from the html, his browser displayed the page correctly... Is this a virus or a new tracking toy developed by Google?
i don't think its tied to clicks. i think its tied to pageviews, because it happens to me only when i've been doing certain types of site updates that require me to do a lot of page refreshes and double checks.