[VB6: UserControl] stupid crash:(

i'm update my sprite control, but ins't the 1st time that i catch stupid bug's or crashes...
i said stupid bug's/crashes, because i build the things and work very well... but when i put soomething new that is ok, i found these stupid bug's/crashes. for resolve these i always must do not everything(because i have another project working) but more or less.
look these code in property page:

Code:

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Private Sub PropertyPage_SelectionChanged()
    txtHeight.Text = SelectedControls(0).StripsHeight
    txtWidth.Text = SelectedControls(0).StripsWidth
    txtPosX.Text = SelectedControls(0).StripsLeft
    txtPosY.Text = SelectedControls(0).StripsTop
    txtImagensLinha = SelectedControls(0).StripsImagesLine
    txtImagensColuna = SelectedControls(0).StripsImagesColumn
    txtSeparaçãoHorizontal.Text = SelectedControls(0).StripsSeparationHorizontal
    txtSeparaçãoVertical.Text = SelectedControls(0).StripsSeparationVertical
    If SelectedControls(0).StripsActivate = True Then
        chkActivarStrips.Value = 1
        SelectedControls(0).ActualSubImage = 1
    Else
        chkActivarStrips.Value = 0
        SelectedControls(0).ActualSubImage = 0
    End If
    MsgBox "Sprite2D: Properties Pages"
    If (UCase(SelectedControls(0).FileName) Like "*.ANI" Or UCase(SelectedControls(0).FileName) Like "*.CUR") Then
        picVisualizar.Picture = SelectedControls(0).Img
    Else
        picVisualizar.Picture = LoadPicture(SelectedControls(0).FileName)
    End If
    Changed = False
End Sub

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i just try put properties for work with API functions...
if i delete the message box, my project(inclued the VB6) crashes, but with it works fine...
why these stupid of bug's/craches?
The VB6 UC section isn't aproved?
thanks