the following works:

		LOCAL ;
			SaveInPath, ;
			VcxName, ;
			ClassName

		SaveInPath	= GetPath("TEMP", .T.)
		VcxName		= SUBS(SYS(2015), 2) + ".vcx"
		ClassName	= "MSChartTempClass"
		THISFORM.Pageframe1.ReportGraph_Page.Chartarea1.SAVEASCLASS(SaveInPath + VcxName, ClassName, "")

		THISFORM.VISIBLE		= .F.
		THISFORM.WINDOWSTATE = 0

		FullSizeDisplay = NEWOBJECT("FullSizeDisplay", THIS.CLASSLIBRARY)
		FullSizeDisplay.NEWOBJECT(ClassName, ClassName, (SaveInPath + VcxName))
		FullSizeDisplay.LOCKSCREEN				= .T.
		FullSizeDisplay.VISIBLE					= .T.
		FullSizeDisplay.oCallingForm			= ThisForm
		FullSizeDisplay.&ClassName..QuerryEnginePointer = THISFORM.Pageframe1.ReportOption_Page.QuerryEngine
		FullSizeDisplay.&ClassName..TOP		= 0
		FullSizeDisplay.&ClassName..LEFT		= 0
		FullSizeDisplay.&ClassName..WIDTH	= FullSizeDisplay.WIDTH
		FullSizeDisplay.&ClassName..HEIGHT	= FullSizeDisplay.HEIGHT
		FullSizeDisplay.&ClassName..VISIBLE	= .T.
		FullSizeDisplay.LOCKSCREEN				= .F.
		FullSizeDisplay.SHOW(1)

		* *** clean up
		CLEAR CLASS (ClassName)
		DELETE FILE (SaveInPath + VcxName)
		DELETE FILE (SaveInPath + JUSTSTEM(VcxName) + ".vct")

		THISFORM.VISIBLE = .T.

obviously i can't use "Clear all" <g> as this would crash my app. the trick here was to "CLEAR CLASS (ClassName)". i guess since i refered to the newly added object in the new form like this: "FullSizeDisplay.&ClassName.." (even though ClassName is not an object but a character) it must be released - oh well.

thanks for all your help!