Black screen cycles render

I have made one of my first blender animations, it is sorta a minecraft render with some moving objects, shadow, sun shining on reflecting water with waves. I outputted it as .PNG but when it was finally done rendering I got a folder full off black images!? I haven’t changed much settings, only some quality changes like resolution, light bounces, samples… So I tried it with the default settings, only lower resolution, and it was still black. Someone checked my .blend file and there seemed to be nothing wrong.
I render with CPU since I can’t seem to select GPU

Some info about my laptop.
HP ProBook
Intel HD Graphics 3000
Intel® Core™ i3-2370M CPU @2.40 GHz (4 CPUs) ~2.40GHz
Blender 2.66a
If you need more, just ask me.

What can I do to sucessfully render it?

So where’s your blend file then ?