1017: The definition of base class UIComponent was not found.
Trying to extends the UIComponent for a new component in action script 3, I’ve got this error. To fix this, I added a new classpath in the ActionScript 3.0 Settings from the Preferences panel. So if you get this error try to add this path: C:\Program Files\Adobe\Adobe Flash CS3\en\Configuration\Component Source\ActionScript 3.0\User Interface