ComboBox scrollbar problem

Hello there, I am having a problem with a dropdown ComboBox. When I open the box up and use the scrollbar, the dropdown automatically closes on me. The dropdown is within another movie as well, if that matters. Does anyone know what is going? I am using Flash 8 for development and it seems to work fine locally when I do Ctrl+Enter, but not in the browser (using a Flash 9 plugin in IE and Firefox).