Most realist theories of war agree that states that are satisfied or otherwise bought-into the international system are unlikely to start conflict or take extreme risks--where those that are unsatisfied are likely to take risks to change the world order. When we look at rising or powerful countries with respect to our security, we ask: are they revisionist? If the answer is clearly no, we get countries like the UK, France, Japan--not a threat, despite being very powerful. With countries like China, Russia, there is serious debate over their love of the status quo.
Great Powers create the international order--the UK, France, Britain, Russia, and China are the 5 permanent members of the security council. The WTO, WHO, the IAEA (keep this one in mind) and dozens of other international organizations were made either by the US or by the EU with US support.
No Great Power (or rising Great Power) has decided that it is no longer a status-quo power since the end of the Cold War. Iran is certainly not a Great Power, but it is a rather powerful regional power, and has spent a great deal of time and effort trying to spread its influence to Iraq, win a power struggle in Lebanon, and boot Israel from the map. In the last few years, the Great Powers have used a combination of coercive and rewarding diplomacy (sticks and carrots) to try and turn Iran to toe the status quo line.
Today, Ahmadinejad has shown that he's not interested. He claimed that the entire global system is "unjust," which is a bad sign--it means he is not terribly interested in trying to use the global system to address his grievances.
His grievances, by brief summary of his speech:
1) The US is "bullying" governments in Iraq and Lebanon into being pro-western, because that would definitely not otherwise be possible.
2) Israel is not yet wiped off the map.
3) The IAEA is still pressuring Iran.
4) The IAEA is not pressuring the US/France/Britain/China/Russia.
The IAEA won't pressure the Great Powers to disarm--it is a construct of the Great Powers. For the same reasons, it won't let up on Iran. Israel is not going away. And whatever bullying the US is now doing that ticks Iran off, it isn't going to stop.
Earlier murmurings that the Iranians might be reaching a deal on Iraq and the nuclear issue seem to have been overly-optimistic. It looks like Iran is taking a stance that dooms it to confrontation.