When I publish a module, ALL the assignments automatically become published as well. As I do not want my students to see the assignments prior to certain dates, I unpublished the module, went in and unpublished the assignments that I did now want shown, then republished the module.
When I did that ALL the assignments (even the ones I had "unpublished" ended up being republished as well!
The only way a I can publish the module AND unpublish certain assignments is to have the module published first, and then quickly unpublish the assignments. I don't like this however, since students have a brief period of time where they can "see" the assignment (even quizzes).