combobox won't function

okay..here is the setup:

i am working on a project that has separate swf files serving as  different sections (students, faculty, etc). for each section, on the  first frame i have a combobox that lists the different values within  that particular section. when a user clicks on the value, it takes them  to the specific frame within that swf.

there are two problems:

1. when the user selects a value, everything functions correctly but an  error is thrown that says:  

TypeError: Error #1009: Cannot access a property or method of a null  object reference.
at fl.containers::BaseScrollPane/drawBackground()
at fl.controls::List/draw()
at fl.core::UIComponent/drawNow()
at fl.controls::List/scrollToIndex()
at fl.controls::SelectableList/scrollToSelected()
at fl.controls::ComboBox/open()
at fl.controls::ComboBox/onToggleListVisibility()

2. when i click on a button that links to each section from the cover  swf, i am directed to the desired page but when i click on the combobox,  the same error is thrown and the combobox does not function at all..

any ideas??