Which object is null, nativeApplication or activeWindow?
I received all kinds of weird errors, so I decided to build a new Project and see when things start to go wrong.
I am using two swc libraries created in Flash CS4 using the FlexComponentKit for Flash CS3.
As soon as I get them involved, errors start occurring.
Maybe that is the problem, because these swc file function propperly in FlexBuilder 3 projects.