There is a difference between initialization and assignment. What you want to do is not initialization, but assignment. But such assignment to array is not possible in C++.
Here is what you can do:
#include <algorithm>
int array [] = {1,3,34,5,6};
int newarr [] = {34,2,4,5,6};
std::copy(newarr, newarr + 5, array);
However, in C++0x, you can do this:
std::vector<int> array = {1,3,34,5,6};
array = {34,2,4,5,6};
Of course, if you choose to use std::vector
instead of raw array.