new timing belt?

I have a renault megane coupe 1.6 16v (2002) (old shape), the timing belt failed last week so i have renewed it, on completion the engine wont start. The engine turns over freely and the cams are turning. I have done a compression test on the engine and all 4 cylinders are reading zero. Is there some sort of safety device that needs reseting or am i going to have to take the head off?
When the belt failed the engine just cut out, there was no loud valve breaking noises. Any help would be greatley appreciated.