On the other hand, I can see the argument that when you ready an action, your turn is essentially over until the triggering action occurs, and then that's your next turn.
Actually, isn't readying an action a standard action? The triggering of the readied action technically complete's your turn.
Without that, it would be impossible to ready a melee attack on a spell caster to interrupt a spell unless you are in the adjacent square, and that does not seem right.
I'm assuming you mean as part of a surprise round. In any normal round, you can always move and ready, and even in a surprise round you could ready an attack with a 5 foot step.
--Axe