asp:dropdownlist error: 'dropdownlist1' selectedvalue unfair since does exist list items

i have asp.net 2.0 web site countless asp:dropdownlist controls.
the dropdownlist control contains customary info city, state, county etc... info.
in offer customary codes site also tradition codes users configure themselves.
for instance animal dropdown competence enclose values dog, cat, fish, ect...

i am popluating dropdownlist sql 2005 list i combined e.g. tblcodes

everything works good users means supplement orders controlling countless dropdownlist controls select equipment list.

the problem occurrs user wants change tradition dropdowns. instance user change verbage
on animal form control dog k9. where problem starts.

for new orders dump down works fine. user retrieved an aged order
i following blunder c# codebehind
"'dropdownlist1' selectedvalue unfair since does exist list items."

what's duty aged method database domain value dog dropdownlist longer dog the list given user altered k9.

any ideas workaround?

is there proceed asp:dropdownlist accept equipment seeded the list?
is there another control i use?