Transparency problems: White overlay boxes if we print the exported pdf

Hey, there,

We are experiencing some problem with InDesign when using objects which have a semi-transparent content on a non-white background.If we export them from InDesign as PDF and print them, we get white boxes instead of transparency.

We can see the boxes if we display the PDF using the OSX preview, but the boxes are not visible when using Acrobat Pro. But the white boxes also get printed.

We already checked that the attributes for that object should be fine. If we open some old file, and copy the content of the new file into the old file, the boxes are gone and the exported PDF is fine.

Does anyone know what the problem with the "new" file is?

Thank you your help!

See attached InDesign file:

http://d7z.de/tmp/index.php?file=transparenzproblem_forum.indd.zip

The exported PDF file:

http://d7z.de/tmp/index.php?file=transparenzreduzierung.pdf