New Post: SetSource with BMP file

This has to do with the WriteableBitmap base class, but I was hoping someone could answer my question:

Why does this code work for PNG and JPG files but not BMP?

      WriteableBitmap wb = new WriteableBitmap(1500, 1500);
      wb.SetSource(fileStream);

For BMP files I get the following error on SetSource: "Attempted to read or write protected memory. This is often an indication that other memory is corrupt."