Dropdownlist event handler isn't firing on user control

[kimberly.walker]

I have a user control with 3 dropdownlist when a user selects the first
listbox based on his/her selection the 2 listbox will load based off
the users selection from the 2nd listbox the 3rd listbox will load. My
problem is the first listbox works but when the user selects the 2nd
listbox the event fires but not in the selectedindexchange event all of
the dropdownlist have autopostback set to true. I have debug and found
that when I select an item in the 2nd listbox it post back to the page
but never fires the dropdownlist2 it does however fires the first
dropdownlist1. Any help will be greatly appreciated.
Thanks