This might sound funny, but this is what is happening:
I have a form with a tab control (tabMain) and 4 tabpages (tpage1, tpage2, tpage3, tpage4) on it. Further on the fourth tabpage (tpage4) i have another tab control (tabSub) with 4 tabpages (tsubpage1, tsubpage2, tsubpage3, tsubpage4) on it...