Hypersmurf
Moderatarrrrh...
Effects with (save ends) and with 'until the end of your turn//Sustain _____:' merely have two ways to end the power.
But that's not how Crown of Madness is phrased.
Hit: 2d6 + Charisma modifier psychic damage.
Miss: Half damage.
Sustain Minor: The target makes a melee basic attack against one of its adjacent allies of your choice (save ends).
We need to look at p278:
Sustained Durations: An effect that has a "sustain standard", a "sustain move", or a "sustain minor" duration lasts as long as you sustain it. Starting on the turn after you create an effect, you sustain the effect by taking the indicated action: a standard action, a move action, or a minor action. (You can sustain an effect once per turn.) Some effects do something, such as attack, when you sustain them. A power's description indicates what happens when you sustain it or let it lapse. At the end of your turn, if you haven't spent the required action to sustain the effect, the effect ends.
So the effect that has a "sustain minor" duration is Crown of Madness.
Starting on the turn after you create Crown of Madness, you sustain Crown of Madness by taking a minor action. At the end of your turn, if you haven't spent the minor action, Crown of Madness ends.
Before the turn after you create Crown of Madness - that is, on the turn you create Crown of Madness - Crown of Madness doesn't end. Sustain only applies starting on the turn after.
So, starting on the turn after you create Crown of Madness, there are two ways for Crown of Madness to end - 1. you don't sustain Crown of Madness on your turn; or 2. the opponent saves on his turn.
Before the turn after you create Crown of Madness, there's no way for Crown of Madness to end - you're not required to sustain it yet, and (save ends) is not yet applicable.
-Hyp.