CImage's save

[Chipmunk Baby]

I save image using CImage class and fail if I mention the path selected from a CFileDialog object
That means I can straightly save the stream with a CImage variable as
m_img.Save(_T("image.png"));

but it seems unable to work with this path
m_img.Save(_T("C:\\Documents\\image.png"));


I have 2 buttons on my dialog, one to save the stream as specified in my first example, and another is to save as in the second. I press the first button to see a file created and press the second one to see nothing.
If I try to get comerror I will see 80004xxx (I forget what xxx is)


Any help please ?????????