Coolbar and Background Image

I posted this in VCL Components but had no replies.

I just converted from Delphi 3 to 4. A form I have with a cool bar has a
background image. Under Delphi 3 the buttons on the coolbar showed the
marble image as part of the the buttons, a transparent look. In Delphi 4 the
image does not show through. It just looks like square buttons on top of the
image. I checked all of the properties but couldn't see anything that has
changed since Delphi 3.

Any ideas on why the image does not show through properly in Delphi 4?