C++ Class with Dynamic Memory Allocation - Why am I getting this error?

I'm making a class called DblArray, and doing basic functions for it. I seem to be getting a problem when compiling, though, as it says "incorrect checksum for freed object - object was probably modified after being freed." I'll post all of my code below, but I think the problem is happening in this function:

void DblArray::insertVal(double n)
{
  if ( size == capacity )
  {
    capacity *= 2;
    double temp[size];

    for ( int i = 0; i < size; i++ )
      temp[i] = data[i];
    delete [] data;
    data = 0;

    data = new double[capacity];
    for ( int i = 0; i < size; i++ )
      data[i] = temp[i];
  }
  size++;
  data[size] = n;
}

The header file is this:

#include <iostream>

#ifndef DBLARRAY_H
#define DBLARRAY_H

class DblArray
{
private:
  long capacity;
  long size;
  double * data;
public:
  DblArray();
  ~DblArray();
  DblArray(const DblArray& d);
  DblArray& operator = (const DblArray& d);

  double operator [] (int i);
  long getCapacity();
  long getSize();
  double getAverage();
  void insertVal(double);
  void removeVal();
};

#endif // DBLARRAY_H

The implementation file is this:

#include "DblArray.h"

DblArray::DblArray()
{
  capacity = 1;
  size = 0;
  data = new double[capacity];
}

DblArray::~DblArray()
{
  capacity = 0;
  size = 0;
  delete [] data;
  data = NULL;
}

DblArray::DblArray(const DblArray& d)
{
  capacity = d.capacity;
  size = d.size;
  data = new double[capacity];

  for ( int i = 0; i < size; i++ )
  {
    data[i] = d.data[i];
  }
}

DblArray& DblArray::operator = (const DblArray& d)
{
  DblArray dNew;
  dNew.capacity = d.capacity;
  dNew.size = d.size;
  dNew.data = new double[capacity];

  for ( int i = 0; i < dNew.size; i++ )
  {
    dNew.data[i] = d.data[i];
  }

  return dNew;
}

double DblArray::operator [] (int i)
{
  return data[i];
}

long DblArray::getCapacity()
{
  return capacity;
}

long DblArray::getSize()
{
  return size;
}

double DblArray::getAverage()
{
  double average = 0;
  for ( int i = 0; i < size; i++ )
  {
    average += data[i];
  }
  average = average / size;

  return average;
}

void DblArray::insertVal(double n)
{
  if ( size == capacity )
  {
    capacity *= 2;
    double temp[size];

    for ( int i = 0; i < size; i++ )
      temp[i] = data[i];
    delete [] data;
    data = 0;

    data = new double[capacity];
    for ( int i = 0; i < size; i++ )
      data[i] = temp[i];
  }
  size++;
  data[size] = n;
}

void DblArray::removeVal()
{
  data[size] = 0;
}

And the driver is this:

#include <iostream>
#include "DblArray.h"

using namespace std;

DblArray print( DblArray );

int main()
{
  //Data abstractions
  DblArray d1;

  //Printing the contents of d1 before testing functions
  print(d1);

  for ( int i = 0; i < 5; i++ )
  {
    d1.insertVal(i);
  }

  //Printing contents of d1 after adding values
  print(d1);

  return 0;
}

//Function to print the contents of each object
DblArray print( DblArray d )
{
  cout << "Capacity:\t" << d.getCapacity() << endl;
  cout << "Size:\t" << d.getSize() << endl;
  cout << "Data:\t" << endl;
  for ( int i = 0; i < d.getSize(); i++ )
  {
    cout << d[i] << "\t";
  }
  cout << "\n";
}