Form submit not firing
You are checking for user access within the form builder function. Make sure that control is going to the actual form by adding a dpm. It is better to check permissions at the menu definition level unless you have a better reason not to do so.

Next try $form['#submit']='cheo_whiteboard_admin_form_submit';

This makes sure that cheo_whiteboard_admin_form_submit is the only form handler function and hence easier for you to debug.