I have a few combo boxes that I'm using a BO to populate them with. The only problem is after they're filled they automatically set themselves to the first item in the combobox. How do I prevent that? I want the combo boxes to remain empty even after they're filled. I want to force the user to make a choice.

On the combo box, set the TopMostItem property on the business object.  You'll need to specify the test to display, such as "<None>" or "<not selected>" and then a value that the combo box can bind back.