Exception fault: ReferenceError: Error #1065: Variable ::_fileSystemType is not defined. -> ?

Hi! I'm stuck with debugging our AIR Application since it does crash very hard. After days of tracking down at least one point where the app crashes on AIR 3.5, 3.7 and AIR 3.8 beta (you see - I tried...).

AIR 3.5 finally reports this console output:

ScrollerTouch.onTargetMouseDown()-F true // A

ScrollerTouch.onTargetMouseDown()-I // B

targetV [object ScrollPane] // C

CRASH! // D

Exception fault: ReferenceError: Error #1065: Variable ::_fileSystemType is not defined.

          at global/trace()[int:49]

          at de.superclass.control::ScrollerTouch/onTargetMouseDown()[/path/to/.../ScrollerTouch.as:381]

          at de.superclass.control::ScrollerTouch/onTargetMouseDown()

The code snipped:

trace("ScrollerTouch.onTargetMouseDown()-F", _scrollHorizontal ); // A

  switch ( _scrollPolicyVertical )

                              {

  caseScrollPolicy.ON:

  trace("ScrollerTouch.onTargetMouseDown()-G");

  _scrollVertical = true;

                                        break;

  caseScrollPolicy.OFF:

  trace("ScrollerTouch.onTargetMouseDown()-H");

  _scrollVertical = false;

                                        break;

  caseScrollPolicy.AUTO:

  trace("ScrollerTouch.onTargetMouseDown()-I"); // B

  default:

                                                  trace( "targetV", targetV ); // C

                                                  try

                                                  {

                                                            trace( "targetV.height", targetV.height );

                                                  }

                                                  catch( e: Error )

                                                  {

                                                            trace( "CRASH!" ); // D

                                                  }

                                                  _scrollVertical = Boolean( targetV.height < targetV.contentHeight ); // line 381

  trace( "targetV.xxx" );

                                                  trace( "targetV.contentHeight", targetV.contentHeight );

return;

}

So accessing targetV.height somehow crashes very hard (app quits) but I have no clue at all. Actually, this code worked for a long time...

So please, what is ::_fileSystemType ?