Combobox Validating and DataBinding issue

Heya. :)

I've got a quirky thing happening with databinding in C#, .NET 2.0, CSLA 2.something, and my databinding.

The user hits a button, i popup a modal, populate some comboboxes on the modal with some lists from my cache of dictionaries, then set the BindingSource.DataSource to my business object. The comboboxes whose lists I've set are showing the initial value in the list, but they're not reporting to the business object that they have an actual value until they're Validated. All I have to do is tab through the entire screen for this to occur and Validation to pass, but what's the proper way to fix this so that the user doesn't have to select something in every one of those comboboxes for the validation to pass, especially since they're showing an initial value from the list they're set to (cosmetically)?

Any help is greatly appreciated. :)