I don't know if this has been adressed here already, but I didn't find a thread about it.
When you bound a Combobox to a DataTable and set combobox sort property to true, the displaytext's are sorted but the values are not and this messes everything up. I think this is a big big bug.
Sorry for my bad english.

ComboBox Sorting Bug
troy2
I've put in a bug to look at this in a future release, but it may well not be fixed (many types of lists, like Arrays, don't allow sorting through a generic "I'm a list that can be sorted" mechanism, so you'd have to gather a huge (and incomplete) list of "_this_ kind of list is sorted _this_ way").