Are you targeting more than one country in your campaign? If so US traffic is generally more competitive so your ad could be low down for a US searcher, but high up for a Canadian searcher.
Couple both of the situations above and you can have wildly fluctuating ad positions in your stats that simply average out as a single position.
Also, if it's a competitive keyword (and I guess it is), remember many webmasters pan down that far to see where their websites are positioned, both Adwords advertisers and search engine optimizers. This results in impressions but no clicks.