Comment 7 for bug 494115

Until this bug is fixed I'd like to share the workaround I found for my particular problem: Export the blurred background as bitmap (set the appropriate DPI), convert the resulting PNG to PDF, export the rest of the document (i.e. without background - use layers to hide it) and merge the two PDFs with pdftk:

pdftk.exe in.pdf background bg.pdf output out.pdf