By the way, my findings were:

if Animation is set to NO before controls are added, they may get lost. This is essentially what you are suggesting, too.

ALSO, if taskpanel is not the foremost control, buttons and stuff may also get lost, however this may or may not be the case, behavior is different from system to system...

It can be Animation property. Change it back to "AnimationYes" and set it As "AnimationSystem" after you create all controls.

It will be fixed in 9.70

Thanks for all the help and support !

I managed to solve the problem now myself although I have no clue why it originally worked on some systems and not on others.

I reduced the code to the essential minimum. Still, on some XP SP2 systems, the button and text field is invisible. Did I do something wrong in the code? Could it be that virus scanners interfere? Again, on most systems things are as expected, but on some systems the control gets lost...

Here's the code:

Private Declare Function InitCommonControls Lib "Comctl32.dll" () As Long

Dim Group1 As TaskPanelGroup
Dim Item As TaskPanelGroupItem

Private Sub Form_Initialize()
    InitCommonControls
End Sub

Private Sub Form_Load()
    Set Group1 = wndTaskPanel.Groups.Add(0, "CheckAccount")

    With Group1
        pb1.Visible = True
        .Special = True
        .IconIndex = 2
        .Expandable = True
       
        .Caption = "Dies ist ein Test"
        .CaptionVisible = True
        .Enabled = True
       
        .Items.Clear
        Set Item = .Items.Add(0, "Dies ist ein Testtext.", xtpTaskItemTypeText, 2)
        Set Item = .Items.Add(1, "Dies ist ein Testtext.", xtpTaskItemTypeText, 2)
        Set Item = .Items.Add(2, "Dies ist ein Testtext.", xtpTaskItemTypeText, 2)
    
        Set .Items.Add(3, "", xtpTaskItemTypeControl).Control = pb1
    End With
End Sub

In addition, the customer now reports getting error messages like "method ~ of ~ failed". It is an XP Home SP2 with all available updates.

The screen shot shows that the custom controls seem to be missing altogether. There is no "blank space" where they should be but instead the panel just looks as if there was no custom controls on that panel.

Any clues anybody?

I have a very strange problem with Task Panel. I use four task panel groups and use picture boxes with buttons inside on each of them to display buttons.

Everything looked right, but now one customer shows me a screen shot where all the buttons are missing. The task panel itself looks alright, but the custom controls on them are gone.

How can that be? What could I do next?