For some reason I am having problems subtracting several shapes from another (See attached file).

My steps so far were: boolean / difference
picked center piece, confirm
select all the other shapes surrounding it
click done / right click

Nothing happens still all individual shapes. I even tried to subtract each piece individually, but it
makes no difference. I ran into the same problem before with a similar situation, it finally worked,
but unfortunately I can't remember the steps ... and actually it was the same initial problem. It
just worked all the sudden, don't know why.

Am I doing something wrong - or is it a bug?