Balloons doesn't visualized

I have a strange problem.
If I put  a planner on a simple form it works, when I use the same planner on a form that is conteined in another form the balloons doesn't work anymore (I change only the parent!)

Software version:
Delphi 2007
TPlanner May, 2010 for Delphi 2007

This is explained here:

Thanks a lot,
now it works