Only a suggestion:
in the VFP9 SP1 I recommend of rewritten the whole code C++ of the PageFrame.

PUBLIC oform1

ACTIVATE  WINDOW "Debug Output"

oform1=NEWOBJECT("form1")
oform1.Show
RETURN

DEFINE CLASS form1 AS form

	Caption = "Activate NODEFAULT MultiBugs"
	Name = "Form1"
	themes = .t.

	ADD OBJECT pageframe1 AS pageframe WITH ;
		PageCount = 2, ;
		Top = 36, ;
		Left = 36, ;
		Width = 241, ;
		Height = 169, ;
		Name = "Pageframe1", ;
		Page1.Caption = "Click here", ;
		Page1.Name = "Page1"
	
	PROCEDURE GotFocus
		KEYBOARD '{TAB}' PLAIN CLEAR
	ENDPROC

	PROCEDURE pageframe1.Page1.Init
		this.AddObject("text","textbox")
		this.Text.visible = .T.
	ENDPROC

	PROCEDURE pageframe1.Page2.Init
		this.AddObject("check","checkbox")
		this.check.visible = .T.
	ENDPROC
	
	PROCEDURE pageframe1.Page1.Activate
		DEBUGOUT PROGRAM()
	ENDPROC

	PROCEDURE pageframe1.Page1.DeActivate
		DEBUGOUT PROGRAM()
	ENDPROC
	
	PROCEDURE pageframe1.Page2.Activate
	*	DEBUGOUT PROGRAM()
		NODEFAULT
	ENDPROC

	PROCEDURE pageframe1.Page2.DeActivate
		DEBUGOUT PROGRAM()
*		NODEFAULT
	ENDPROC

ENDDEFINE

* Move the mouse over the Tab#1
* - TextBox overdrawed

* Click on Tab#1 => 
* - ActivePage.Deactivate fired

* Click on Tab#2 =>
* There are so so many bugs, that I don't know from whether to begin
*However it can be reassumed, with:  
* NODEFAULT is not supported in PageFrame.Activate

PUBLIC oform1

ACTIVATE  WINDOW "Debug Output"


oform1=NEWOBJECT("form1")
oform1.Show
RETURN

DEFINE CLASS form1 AS form

	Caption = "Activate NODEFAULT MultiBugs"
	Name = "Form1"
	themes = .t.

	ADD OBJECT pageframe1 AS pageframe WITH ;
		PageCount = 2, ;
		Top = 36, ;
		Left = 36, ;
		Width = 241, ;
		Height = 169, ;
		Name = "Pageframe1", ;
		Page1.Caption = "Click here", ;
		Page1.Name = "Page1"
	
	PROCEDURE GotFocus
		DEBUGOUT PROGRAM()
	ENDPROC

	PROCEDURE pageframe1.Page1.Click
		DEBUGOUT PROGRAM()
	ENDPROC

	PROCEDURE pageframe1.Page2.Click
		DEBUGOUT PROGRAM()
	ENDPROC
		
	PROCEDURE pageframe1.Page1.Activate
		DEBUGOUT PROGRAM()
	ENDPROC

	PROCEDURE pageframe1.Page1.DeActivate
		DEBUGOUT PROGRAM()," WITH NODEFAULT"

		NODEFAULT
	ENDPROC
	
	PROCEDURE pageframe1.Page2.Activate
		DEBUGOUT PROGRAM()
	ENDPROC

	PROCEDURE pageframe1.Page2.DeActivate
		DEBUGOUT PROGRAM()

	ENDPROC

ENDDEFINE

* Click on Tab#2 =>
* Bug1: Page2.click fired
* Bug2: Form.Gotfocus fired