Each option in a list box has two values -- a stored value, and a display value. If all of the stored values are identical, the last match is chosen... thus you see the last display value. It doesn't know which display value to match to the identical stored values, so you end up getting the last one selected (which is the expected default behvaior).

I have a problem where I have created a cascading list box from a SQL table.
However,  I am having trouble after I select my data from the list, once I
click away my selection changes to the last item in my drop down list.  Any
advice would be greatly appreciated.

Thank you