Kobayashi - 12:53 am on Dec 12, 2011 (gmt 0)
I have experienced a similar thing. The problem was the order in which Google determined all these factors. In my testing, I had two campaigns targetting different countries with the same keyword at the same max CPC and one of the two keyword statuses would often show another one of your ads is showing for this keyword when it was not. In other words, it was like they determined the ad in my account with the best ad rank first, and THEN looked at targeting criteria for that campaign like which country was targeted instead of doing those things first. If the ad with the highest ad rank happened to be in a campaign that targeted a country that was not where the searcher was no ad would get shown.