Strange behavior !! if there is "something else" going on here. It will be probably a "twist" of a
MODAL form and a "non values/controlsources" for your comboboxes.
Let's change some default properties for your comboboxes.. Why don't you populate it on the INIT method too.. I believe it will be a nice try !!
"Now to him who is able to do immeasurably more than all we ask or imagine, according to his power that is at work within us, Ephesians 3:20