Drat - my alternative (hacking a Firefox extension) sort of worked, but it was too clunky for general use. I'd actually rather just save the PDF and open it manually in Acrobat Reader, it was that bad. Oh, well.
Incidentally, I know why the problem happens, and why it's only visible in Firefox. I'll spare you the technical explanation, but it's not something SunshineMeadows can fix in her role as the forum administrator.