Flash UI Components—oddity

I am experiencing the oddest UI comboBox problem… I have a dropdown that’s being populated from an XML file. If you click on the component to drop down the list and then (before selecting any option) hit any key on the keyboard… the dropdown clears itself and becomes empty. Does anyone know what’s going on? Is there a way to prevent that from happening? Or alternatively, can you disable keyboard feedback? Please help if you can.