Excel 2007 : Grouping and collapsing data

Hi there,

I've got a problem with grouping and collapsing data.
I've got a schedule of more than 3000 items and I wanted to group the data into the susections. That part was not a biggie.
However, I encountered a problem when I was trying to collapse the group. Please have a look at the attachment. Say I want to collapse section 2.1 and that is not a problem. But then I cannot collapse section 2.2. although it has been groupes.

Can someone advise?

Thanks a lot,

K.