Omega theme displays field that has been set to "hidden"

I added an Image field to the Basic Page content type. I want to display the image with the CCK Blocks module, so I went to "Manage Display" and set the format to "Hidden" for the Image field in Default. Then, on the CCK Blocks page (under "Manage Display"), I set the format to Image and the Image Style to a preset (960x300).

Then I set up the CCK Block to display in the Preface First region.

With this setup, I should see the image only once on the page. However, in the Omega theme, it displays twice: Once in the CCK block and once in the node.

This is apparently a problem only in Omega; I tried switching to the Bartik theme, which handled the hidden field correctly (by not displaying it).

I'd appreciate any suggestions about how to fix this. Thanks.