In Flash MX 2004, some of the component code hints are not listed in AsCodeHints.xml or UIComponents.xml. As a result, what used to be a common thing to do in MX by using code hints such as _cb for ComboBox, does not work now.
Well, there are two solutions:
1) Add you own code hints information to the two files mentioned above.
2) Reference the component class in your code:
Now when you type sp. the list of ScrollPane methods and property is displayed!
Thanks go to Rebecca Sun of Macromedia for this tip.