I agree with what Igor wrote.  You could also use scoped array and change your code thus:

#include <boost/scoped_array.hpp>
typedef unsigned char byte;
int main()
{
  boost::scoped_array<byte> buff[10];
  for(int i=0; i<10; i++)
  {
    int size = 2*i + 100;
    buff[i].reset(new byte[size]);
  }

}

HTH,

Nate

P.S. std::unique_ptr<byte[]> could also fit your needs, if that's available with your compiler.