Hi everyone!
Here is a such a strange thing...
If you have a timer on your form and call another form from first one, form which has a combo box, combo box does not work properly.
Item in combo box can not be choosen as it's you wish.
When you got rid from timer everything is fine. But I really need a timer. All I could do is create my own combo by crossing textbox, pushbutton and popup menu which is very stupid. May be you have more wise solution.