It looks like something's wrong with this build (agslib-3.4-2013-06-30.swc). It still asks (throws error) for mx.swc (mx.controls.DateField). It wasn't the case with 3.3 - it shouldn't be needed?
I don't use AttributeInspector nor any custom skins. The error triggers right after runtime initialization, no matter if any map component is used in code.