My first inclination would be to answer the first question with a clear "YES". But come to think of it, the causes of war really have not changed at all, or at least very little. Rather than changes, there has been a shift in the causes. The cause of war which has dominated the last 50 years was the cause of ideology. However, due to the recent end of the Cold War, this cause of war, has significantly declined and is almost trivial.
The causes of war have shifted from mainly ideological ones to economic, ethnic and others. Although these reasons have always played a role as causes of war throughout history, they were in the last 50 years overshadowed by the cause of ideology. Now, with ideology not on top of the agenda anymore, these causes have regained their importance.
After the second World War the world was dominated by two superpowers; the USA and the USSR.
The Cold War was a result of this division of power and of the important policy of spheres of influence. In the post WWII-era the Americans thought that the Russians were aiming to incorporate Western Europe (the US & British sphere of influence) into their sphere of influence (Eastern Europe) by supporting the communists in these countries. Their fears were enforced when a "coup substituted communist for coalition rule in Prague." (Calvocoressi, p.15)(even though this is an Eastern European Country, the fact that a coup was staged against a democratic government is reason enough to raise their fears).
In this ideologically hostile environment the Cold War began. It was characterised by the arms race between the two superpowers who were eager to preserve their spheres of influence. Both developed such powerful weapons which were too dangerous to be used...