WinForms do not cope well with openCV from my experience, but try to watch on the following things, which helped me out.
- In order to cope between data and form, paste all your processing of openCV inside the header. It is indeed a weird way of working, but it is a Microsoft thing...
- Do not add on top of your code the line using namespace cv, it will screw up your functions. Instead, call each openCV function by adding cv::FunctionName.
- Check your includes again, there is a big chance you have a typo somewhere in your list.
- Did you use the debug libraries in release mode or vice versa?
Get back at me if more problems arise, maybe add a link to a pastebin of your code?