Debug Assertion Failed Expression: _pFirstBlock == pHead using OpenCV and C++ trying to call SurfFeatureDetector

I have this function in C++ using OpenCV:

vector<KeyPoint> test(Mat img)
{
  int minHessian = 400;
  SurfFeatureDetector detector( minHessian );

  vector<KeyPoint> vKeypoints;
  detector.detect( img, vKeypoints );

  return vKeypoints;
}

When I call this function in my main-method everything works fine.

int main( int, char** argv )
{
    // path to a image-file
    char* input = "image.jpg";

    // read image into Mat img
    Mat img = imread( input, CV_LOAD_IMAGE_GRAYSCALE );

    // call function test
    test(img);

    waitKey(0);
    return 0;
}

But as soon as I'm calling this method twice...

int main( int, char** argv )
{
    // path to a image-file
    char* input = "image.jpg";

    // read image into Mat img
    Mat img = imread( input, CV_LOAD_IMAGE_GRAYSCALE );

    // call function test
    test(img);
    test(img); // <-- !!! second call

    waitKey(0);
    return 0;
}

...I get the following error:

Can anyone tell me where my mistake is and how I could fix this? I need to call this function twice with two different images, but every time I do this I get this error.

I'm using Visual Studio 2012.

I've found my mistake. I accidentally copied the openCV-dlls of the VC12 folder, because I forgot that Visual Studio 2012 is VC11. Now it works. Maybe this will help someone else who has the same problem and copied the dlls of the wrong folder.