If you have a combox in a swf, and load that swf into a wrapper swf, it's POSSIBLE the green halo will stick around long after you scroll and make a selection.
Simply add this to your actionscript_
yourComboBox.drawFocus = ""; yourComboBox.dropdown.drawFocus="";
That should disable it. There. That's a headache I hope I can spare you. I can't tell you how long I worked with "_focusrect" and "focusRectEnabled" before find that solution.