euh, utnik, i'm not sure that exporting to pdf 1.3 and having a look at the output will really help.
if you export to pdf 1.3 you might get a warning that a specific element does contain a transparency, which indeed could help MOsMemoir track her issue.
but if you ignore the warning (or scribus does not detect the issue), as far as i know look at the pdf output will not help in any way...
or am i missing something?