In brief, Qatar has been squabbling with the other Arab states (UAE, Kuwait, Saudi Arabia, Bahrain) over a variety of issues, primarily resentment of Al Jazeera, Qatar's state-sponsored news network, and concern over Qatar's close relationship with Iran and the Muslim Brotherhood.
Things came to a head recently, when the other Arab nations declared an embargo on Qatar, which is land-locked and relies nearly 100% on imported food.
What I meant to say is that it is hemmed in by land, since its only land border is with Saudi Arabia, who are leading the boycott. And, Qatar doesn't have any deep-water ports.