The hefty loans the U.S. gave Turkey, loans that had nothing (wink wink) to do with the war in Iraq, are evidently insufficient to keep the Turkish government happy. It could be that U.S. air raids on a northern Iraqi city with ethnic ties to Turkey soured the deal.
Tal Afar is overrun with terrorists, the Pentagon says, hence the stern U.S. response. Turks see the hands of their enemies the Kurds at work, setting the U.S. against any and all non-Kurdish centers of power with self-serving "intelligence" reports.
In short, another fine mess.