Found an issue in Flex Viewer 2.0 beta2 classic menu. When user rolls over menu, menu is shown. But when users tries to click on menu item - it hides as mouse rolls out from controller menu.
file "ControllerMenu.mxml" line
<mx:VRule styleName="ControllerRule" height="15"/>
should be changed to at least
<mx:VRule styleName="ControllerRule" height="15" width="40"/>
