VerifyError: Error #1053: Illegal override of removeChildBridge in mx.managers.S

Ran into this error recently when using automation testing (RunTimeLoading.html/swf).

Turned out to be a recently updated SWC (library) that was compiled under a newer SDK than the main app.

With the mixed SDKs main app / SWC(s) RunTimeLoading.swf was unable to load regardless of which SDK version RunTimeLoading was compiled under.