Hey Jerry,
First of all, don't bind a ComboBox to the .Text property, bind to .SelectedValue. That will probably take care of every problem you're having. I didn't realize that you were binding to the .Text property.
As far as Unbinding and Rebinding goes, all you really have to do is Remove an existing Binding in the Unbind() and put it back in the Rebind(). Again, as I said in my previous post, this is only a problem (or at least where I've seen it as a problem) when *manually* moving the BindingContext's .Position. If you're not doing that, then you don't have to worry about it.
~~Bonnie