Error Microsoft C++ exception: mwException at memory location when passing CString to Matlab function

I passed the path of file to the Matlab function, so it can read it. However, I got crashed again. Here what I did:

in Matlab:

function ImgProc(pathname)
mov=VideoReader(pathname);
nFrames=mov.NumberOfFrames;

for k=1:10
img=read(mov,k);
img=rgb2gray(img);
img = imresize(img, [64, 64]);
imshow(img);

code in C++: sFileName is CString which contains the video file path.

CFileDialog dlgFile(TRUE, NULL, NULL, OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, _T("Movie Files (*.avi;*.mpg;*.mp4)|*.avi;*.mpg;*.mp4||"), this);
CString sFileName  = dlgFile.GetPathName();
bool a=mclInitializeApplication(NULL,0);
    bool b= ImgProcInitialize();
    mwArray out(sFileName);
    ImgProc(out);
    ImgProcTerminate();
    mclTerminateApplication();

ImgProc function in C++:

ImgProc(const mwArray& pathname);
please help